import java.io.*;
import java.math.*;
import java.util.*;
public class Main
{
	static class FastReader
    {
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public FastReader() { this(System.in); }public FastReader(InputStream is) { mIs = is;}
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];}
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;}
        public String next(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();}
        public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;}
        public int i(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;}
        public double d() throws IOException {return Double.parseDouble(next()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; }
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; }
        public void scanIntArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i();}}
        public void scanIntIndexArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}}
        public void scanLongArr(long [] arr){for (int i=0;i<arr.length;++i){arr[i]=l();}}
        public void shuffle(int [] arr){ for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } }
        public int swapIntegers(int a,int b){return a;} //Call it like this: a=swapIntegers(b,b=a)
    }
	public static void main(String args[]) throws IOException{
		FastReader in = new FastReader();
		PrintWriter pw = new PrintWriter(System.out);
		StringBuilder out = new StringBuilder();
		int k = in.i(), a= in.i(), b=in.i();
		int v = (a/k+1)*k;
		if(a%k==0 || b%k==0 || (v>a && v<b))
			out.append("OK");
		else
			out.append("NG");
		pw.print(out);
		pw.flush();
        pw.close();
	}
	private static class Pair<F, S> {
 
        public F first;
 
        public S second;
 
        public Pair() {}
 
        public Pair(F first, S second) {
            this.first = first;
            this.second = second;
        }
		public String toString(){
			return "("+first+", "+second+")";
		}
    }
 
    private static class Triple<F, S, T> {
 
        public F first;
 
        public S second;
 
        public T third;
 
        public Triple() {}
 
        public Triple(F first, S second, T third) {
            this.first = first;
            this.second = second;
            this.third = third;
        }
    }
}
		// long k = in.i();
		// long lo = 0, hi = (long)100000;
		// while(lo<hi){
			// long mid = lo+(hi-lo)/2;
			// if((long)100*Math.pow(1.01,mid)>=k) hi=mid;
			// else lo = mid+1;
			// System.out.println(100*Math.pow(1.01,mid));
		// } import java.io.*; io.* java import java.math.*; math.* java import java.util.*; util.* java public class Main
{
	static class FastReader
    {
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public FastReader() { this(System.in); }public FastReader(InputStream is) { mIs = is;}
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];}
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;}
        public String next(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();}
        public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;}
        public int i(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;}
        public double d() throws IOException {return Double.parseDouble(next()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; }
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; }
        public void scanIntArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i();}}
        public void scanIntIndexArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}}
        public void scanLongArr(long [] arr){for (int i=0;i<arr.length;++i){arr[i]=l();}}
        public void shuffle(int [] arr){ for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } }
        public int swapIntegers(int a,int b){return a;} //Call it like this: a=swapIntegers(b,b=a)
    }
	public static void main(String args[]) throws IOException{
		FastReader in = new FastReader();
		PrintWriter pw = new PrintWriter(System.out);
		StringBuilder out = new StringBuilder();
		int k = in.i(), a= in.i(), b=in.i();
		int v = (a/k+1)*k;
		if(a%k==0 || b%k==0 || (v>a && v<b))
			out.append("OK");
		else
			out.append("NG");
		pw.print(out);
		pw.flush();
        pw.close();
	}
	private static class Pair<F, S> {
 
        public F first;
 
        public S second;
 
        public Pair() {}
 
        public Pair(F first, S second) {
            this.first = first;
            this.second = second;
        }
		public String toString(){
			return "("+first+", "+second+")";
		}
    }
 
    private static class Triple<F, S, T> {
 
        public F first;
 
        public S second;
 
        public T third;
 
        public Triple() {}
 
        public Triple(F first, S second, T third) {
            this.first = first;
            this.second = second;
            this.third = third;
        }
    }
} Main public static void main(String args[]) throws IOException{
		FastReader in = new FastReader();
		PrintWriter pw = new PrintWriter(System.out);
		StringBuilder out = new StringBuilder();
		int k = in.i(), a= in.i(), b=in.i();
		int v = (a/k+1)*k;
		if(a%k==0 || b%k==0 || (v>a && v<b))
			out.append("OK");
		else
			out.append("NG");
		pw.print(out);
		pw.flush();
        pw.close();
	} main {
		FastReader in = new FastReader();
		PrintWriter pw = new PrintWriter(System.out);
		StringBuilder out = new StringBuilder();
		int k = in.i(), a= in.i(), b=in.i();
		int v = (a/k+1)*k;
		if(a%k==0 || b%k==0 || (v>a && v<b))
			out.append("OK");
		else
			out.append("NG");
		pw.print(out);
		pw.flush();
        pw.close();
	} FastReader in = new FastReader(); in new FastReader() PrintWriter pw = new PrintWriter(System.out); pw new PrintWriter(System.out) StringBuilder out = new StringBuilder(); out new StringBuilder() int k = in.i() k in.i() in.i in a= in.i() a in.i() in.i in b=in.i(); b in.i() in.i in int v = (a/k+1)*k; v (a/k+1)*k (a/k+1) a/k a k 1 k if(a%k==0 || b%k==0 || (v>a && v<b))
			out.append("OK");
		else
			out.append("NG"); a%k==0 || b%k==0 || (v>a && v<b) a%k==0 || b%k==0 || (v>a && v<b) a%k==0 a%k a k 0 b%k==0 b%k b k 0 (v>a && v<b) v>a v a v<b v b out.append("OK") out.append out "OK" out.append("NG") out.append out "NG" pw.print(out) pw.print pw out pw.flush() pw.flush pw pw.close() pw.close pw String args[] args static class FastReader
    {
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public FastReader() { this(System.in); }public FastReader(InputStream is) { mIs = is;}
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];}
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;}
        public String next(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();}
        public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;}
        public int i(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;}
        public double d() throws IOException {return Double.parseDouble(next()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; }
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; }
        public void scanIntArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i();}}
        public void scanIntIndexArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}}
        public void scanLongArr(long [] arr){for (int i=0;i<arr.length;++i){arr[i]=l();}}
        public void shuffle(int [] arr){ for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } }
        public int swapIntegers(int a,int b){return a;} //Call it like this: a=swapIntegers(b,b=a)
    } FastReader private InputStream mIs; mIs private byte[] buf = new byte[1024]; buf new byte[1024] 1024 private int curChar curChar numChars; numChars public FastReader() { this(System.in); } FastReader { this(System.in); } this(System.in) this System.in System System.in public FastReader(InputStream is) { mIs = is;} FastReader { mIs = is;} mIs = is mIs is InputStream is is public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];} read {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];} if (numChars == -1) throw new InputMismatchException(); numChars == -1 numChars -1 1 throw new InputMismatchException(); new InputMismatchException() if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; } curChar >= numChars curChar numChars {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; } curChar = 0 curChar 0 try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();} catch (IOException e) { throw new InputMismatchException();} IOException e { throw new InputMismatchException();} throw new InputMismatchException(); new InputMismatchException() { numChars = mIs.read(buf);} numChars = mIs.read(buf) numChars mIs.read(buf) mIs.read mIs buf if (numChars <= 0) return -1; numChars <= 0 numChars 0 return -1; -1 1 return buf[curChar++]; buf[curChar++] buf curChar++ curChar public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;} nextLine {int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;} int c = read(); c read() read while (isSpaceChar(c)) c = read(); isSpaceChar(c) isSpaceChar c c = read() c read() read StringBuilder res = new StringBuilder(); res new StringBuilder() do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c)); !isEndOfLine(c) isEndOfLine(c) isEndOfLine c {res.appendCodePoint(c);c = read();} res.appendCodePoint(c) res.appendCodePoint res c c = read() c read() read return res.toString() ; res.toString() res.toString res public String next(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();} next {int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();} int c = read(); c read() read while (isSpaceChar(c)) c = read(); isSpaceChar(c) isSpaceChar c c = read() c read() read StringBuilder res = new StringBuilder(); res new StringBuilder() do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {res.appendCodePoint(c);c = read();} res.appendCodePoint(c) res.appendCodePoint res c c = read() c read() read return res.toString(); res.toString() res.toString res public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;} l {int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;} int c = read(); c read() read while (isSpaceChar(c)) c = read(); isSpaceChar(c) isSpaceChar c c = read() c read() read int sgn = 1; sgn 1 if (c == '-') { sgn = -1 ; c = read() ; } c == '-' c '-' { sgn = -1 ; c = read() ; } sgn = -1 sgn -1 1 c = read() c read() read long res = 0; res 0 do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c { if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();} if (c < '0' || c > '9') throw new InputMismatchException(); c < '0' || c > '9' c < '0' c '0' c > '9' c '9' throw new InputMismatchException(); new InputMismatchException() res *= 10 res 10 res += c - '0' res c - '0' c '0' c = read() c read() read return res * sgn; res * sgn res sgn public int i(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;} i {int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;} int c = read() ; c read() read while (isSpaceChar(c)) c = read(); isSpaceChar(c) isSpaceChar c c = read() c read() read int sgn = 1; sgn 1 if (c == '-') { sgn = -1 ; c = read() ; } c == '-' c '-' { sgn = -1 ; c = read() ; } sgn = -1 sgn -1 1 c = read() c read() read int res = 0; res 0 do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c)); !isSpaceChar(c) isSpaceChar(c) isSpaceChar c {if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;} if (c < '0' || c > '9') throw new InputMismatchException(); c < '0' || c > '9' c < '0' c '0' c > '9' c '9' throw new InputMismatchException(); new InputMismatchException() res *= 10 res 10 res += c - '0' res c - '0' c '0' c = read() c read() read return res * sgn; res * sgn res sgn public double d() throws IOException {return Double.parseDouble(next()) ;} d {return Double.parseDouble(next()) ;} return Double.parseDouble(next()) ; Double.parseDouble(next()) Double.parseDouble Double next() next public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; } isSpaceChar { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; } return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1 c == '\t' c == '\r' c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1 c == ' ' c ' ' c == '\n' c '\n' c == '\r' c '\r' c == '\t' c '\t' c == -1 c -1 1 int c c public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; } isEndOfLine { return c == '\n' || c == '\r' || c == -1; } return c == '\n' || c == '\r' || c == -1; c == '\n' || c == '\r' || c == -1 c == '\n' || c == '\r' || c == -1 c == '\n' c '\n' c == '\r' c '\r' c == -1 c -1 1 int c c public void scanIntArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i();}} scanIntArr { for(int li=0;li<arr.length;++li){ arr[li]=i();}} for(int li=0;li<arr.length;++li){ arr[li]=i();} int li=0; int li=0; li 0 li<arr.length li arr.length arr arr.length ++li ++li li { arr[li]=i();} { arr[li]=i();} arr[li]=i() arr[li] arr li i() i int [] arr arr public void scanIntIndexArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}} scanIntIndexArr { for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}} for(int li=0;li<arr.length;++li){ arr[li]=i()-1;} int li=0; int li=0; li 0 li<arr.length li arr.length arr arr.length ++li ++li li { arr[li]=i()-1;} { arr[li]=i()-1;} arr[li]=i()-1 arr[li] arr li i()-1 i() i 1 int [] arr arr public void scanLongArr(long [] arr){for (int i=0;i<arr.length;++i){arr[i]=l();}} scanLongArr {for (int i=0;i<arr.length;++i){arr[i]=l();}} for (int i=0;i<arr.length;++i){arr[i]=l();} int i=0; int i=0; i 0 i<arr.length i arr.length arr arr.length ++i ++i i {arr[i]=l();} {arr[i]=l();} arr[i]=l() arr[i] arr i l() l long [] arr arr public void shuffle(int [] arr){ for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } } shuffle { for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } } for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } int i=arr.length; int i=arr.length; i arr.length arr arr.length i>0 i 0 --i --i i { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } int r=(int)(Math.random()*i); r (int)(Math.random()*i) Math.random() Math.random Math i int temp=arr[i-1]; temp arr[i-1] arr i-1 i 1 arr[i-1]=arr[r] arr[i-1] arr i-1 i 1 arr[r] arr r arr[r]=temp arr[r] arr r temp int [] arr arr public int swapIntegers(int a,int b){return a;} //Call it like this: a=swapIntegers(b,b=a) swapIntegers {return a;} return a; a int a a int b b private static class Pair<F, S> {
 
        public F first;
 
        public S second;
 
        public Pair() {}
 
        public Pair(F first, S second) {
            this.first = first;
            this.second = second;
        }
		public String toString(){
			return "("+first+", "+second+")";
		}
    } Pair public F first; first public S second; second public Pair() {} Pair {} public Pair(F first, S second) {
            this.first = first;
            this.second = second;
        } Pair {
            this.first = first;
            this.second = second;
        } this.first = first this.first this this.first first this.second = second this.second this this.second second F first first S second second public String toString(){
			return "("+first+", "+second+")";
		} toString {
			return "("+first+", "+second+")";
		} return "("+first+", "+second+")"; "("+first+", "+second+")" second ", " "("+first+", "+second+")" "(" first ", " second ")" private static class Triple<F, S, T> {
 
        public F first;
 
        public S second;
 
        public T third;
 
        public Triple() {}
 
        public Triple(F first, S second, T third) {
            this.first = first;
            this.second = second;
            this.third = third;
        }
    } Triple public F first; first public S second; second public T third; third public Triple() {} Triple {} public Triple(F first, S second, T third) {
            this.first = first;
            this.second = second;
            this.third = third;
        } Triple {
            this.first = first;
            this.second = second;
            this.third = third;
        } this.first = first this.first this this.first first this.second = second this.second this this.second second this.third = third this.third this this.third third F first first S second second T third third public class Main
{
	static class FastReader
    {
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public FastReader() { this(System.in); }public FastReader(InputStream is) { mIs = is;}
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];}
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;}
        public String next(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();}
        public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;}
        public int i(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;}
        public double d() throws IOException {return Double.parseDouble(next()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; }
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; }
        public void scanIntArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i();}}
        public void scanIntIndexArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}}
        public void scanLongArr(long [] arr){for (int i=0;i<arr.length;++i){arr[i]=l();}}
        public void shuffle(int [] arr){ for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } }
        public int swapIntegers(int a,int b){return a;} //Call it like this: a=swapIntegers(b,b=a)
    }
	public static void main(String args[]) throws IOException{
		FastReader in = new FastReader();
		PrintWriter pw = new PrintWriter(System.out);
		StringBuilder out = new StringBuilder();
		int k = in.i(), a= in.i(), b=in.i();
		int v = (a/k+1)*k;
		if(a%k==0 || b%k==0 || (v>a && v<b))
			out.append("OK");
		else
			out.append("NG");
		pw.print(out);
		pw.flush();
        pw.close();
	}
	private static class Pair<F, S> {
 
        public F first;
 
        public S second;
 
        public Pair() {}
 
        public Pair(F first, S second) {
            this.first = first;
            this.second = second;
        }
		public String toString(){
			return "("+first+", "+second+")";
		}
    }
 
    private static class Triple<F, S, T> {
 
        public F first;
 
        public S second;
 
        public T third;
 
        public Triple() {}
 
        public Triple(F first, S second, T third) {
            this.first = first;
            this.second = second;
            this.third = third;
        }
    }
} public class Main
{
	static class FastReader
    {
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public FastReader() { this(System.in); }public FastReader(InputStream is) { mIs = is;}
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];}
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;}
        public String next(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();}
        public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;}
        public int i(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;}
        public double d() throws IOException {return Double.parseDouble(next()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; }
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; }
        public void scanIntArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i();}}
        public void scanIntIndexArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}}
        public void scanLongArr(long [] arr){for (int i=0;i<arr.length;++i){arr[i]=l();}}
        public void shuffle(int [] arr){ for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } }
        public int swapIntegers(int a,int b){return a;} //Call it like this: a=swapIntegers(b,b=a)
    }
	public static void main(String args[]) throws IOException{
		FastReader in = new FastReader();
		PrintWriter pw = new PrintWriter(System.out);
		StringBuilder out = new StringBuilder();
		int k = in.i(), a= in.i(), b=in.i();
		int v = (a/k+1)*k;
		if(a%k==0 || b%k==0 || (v>a && v<b))
			out.append("OK");
		else
			out.append("NG");
		pw.print(out);
		pw.flush();
        pw.close();
	}
	private static class Pair<F, S> {
 
        public F first;
 
        public S second;
 
        public Pair() {}
 
        public Pair(F first, S second) {
            this.first = first;
            this.second = second;
        }
		public String toString(){
			return "("+first+", "+second+")";
		}
    }
 
    private static class Triple<F, S, T> {
 
        public F first;
 
        public S second;
 
        public T third;
 
        public Triple() {}
 
        public Triple(F first, S second, T third) {
            this.first = first;
            this.second = second;
            this.third = third;
        }
    }
} Main
import java.io.*;
import java.math.*;
import java.util.*;
public class Main
{
	static class FastReader
    {
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public FastReader() { this(System.in); }public FastReader(InputStream is) { mIs = is;}
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];}
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;}
        public String next(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();}
        public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;}
        public int i(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;}
        public double d() throws IOException {return Double.parseDouble(next()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; }
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; }
        public void scanIntArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i();}}
        public void scanIntIndexArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}}
        public void scanLongArr(long [] arr){for (int i=0;i<arr.length;++i){arr[i]=l();}}
        public void shuffle(int [] arr){ for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; } }
        public int swapIntegers(int a,int b){return a;} //Call it like this: a=swapIntegers(b,b=a)
    }
	public static void main(String args[]) throws IOException{
		FastReader in = new FastReader();
		PrintWriter pw = new PrintWriter(System.out);
		StringBuilder out = new StringBuilder();
		int k = in.i(), a= in.i(), b=in.i();
		int v = (a/k+1)*k;
		if(a%k==0 || b%k==0 || (v>a && v<b))
			out.append("OK");
		else
			out.append("NG");
		pw.print(out);
		pw.flush();
        pw.close();
	}
	private static class Pair<F, S> {
 
        public F first;
 
        public S second;
 
        public Pair() {}
 
        public Pair(F first, S second) {
            this.first = first;
            this.second = second;
        }
		public String toString(){
			return "("+first+", "+second+")";
		}
    }
 
    private static class Triple<F, S, T> {
 
        public F first;
 
        public S second;
 
        public T third;
 
        public Triple() {}
 
        public Triple(F first, S second, T third) {
            this.first = first;
            this.second = second;
            this.third = third;
        }
    }
}
		// long k = in.i();
		// long lo = 0, hi = (long)100000;
		// while(lo<hi){
			// long mid = lo+(hi-lo)/2;
			// if((long)100*Math.pow(1.01,mid)>=k) hi=mid;
			// else lo = mid+1;
			// System.out.println(100*Math.pow(1.01,mid));
		// }