import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.NoSuchElementException;

public class Main {
    // template start ---8<-----------8<---
	FastScanner sc = new FastScanner(System.in);
	static PrintWriter out;

	public static void main(String[] args) throws IOException {
		out = new PrintWriter(System.out);
		new Main().solve();
		out.flush();
	}
	// template end ---8<-----------8<---

	void solve() {
		int X = sc.nextInt();
		boolean[] expo = new boolean[X+1];

		expo[1] = true;
		for (int b=2;b<=X;b++) {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		}
		for (int i=X; i>=0;i--){
			if (expo[i]) {
				out.println(i);
				return;
			}
		}



	}

    // template start ---8<-----------8<---
	class FastScanner {
		private final InputStream in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		FastScanner(InputStream in) {
			this.in = in;
		}

		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		}

		private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		}

		public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}

		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}
	}

	class Random {
		private long seed;
		private final long multiplier = 0x5DEECE66DL, addend = 0xBL, mask = (1L << 48) - 1;
		int bits, val;

		Random(long seed) {
			this.seed = seed;
		}

		int nextInt(int n) {
			do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0);
			return val;
		}

		double nextDouble() {
			return nextInt(10000000) / 10000000.0;
		}
	}

	final double TEMP = 10;
	static final long TL = 5850;
	static boolean submit = true;
    // template end ---8<-----------8<---

}
 import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.NoSuchElementException; NoSuchElementException java.util public class Main {
    // template start ---8<-----------8<---
	FastScanner sc = new FastScanner(System.in);
	static PrintWriter out;

	public static void main(String[] args) throws IOException {
		out = new PrintWriter(System.out);
		new Main().solve();
		out.flush();
	}
	// template end ---8<-----------8<---

	void solve() {
		int X = sc.nextInt();
		boolean[] expo = new boolean[X+1];

		expo[1] = true;
		for (int b=2;b<=X;b++) {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		}
		for (int i=X; i>=0;i--){
			if (expo[i]) {
				out.println(i);
				return;
			}
		}



	}

    // template start ---8<-----------8<---
	class FastScanner {
		private final InputStream in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		FastScanner(InputStream in) {
			this.in = in;
		}

		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		}

		private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		}

		public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}

		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}
	}

	class Random {
		private long seed;
		private final long multiplier = 0x5DEECE66DL, addend = 0xBL, mask = (1L << 48) - 1;
		int bits, val;

		Random(long seed) {
			this.seed = seed;
		}

		int nextInt(int n) {
			do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0);
			return val;
		}

		double nextDouble() {
			return nextInt(10000000) / 10000000.0;
		}
	}

	final double TEMP = 10;
	static final long TL = 5850;
	static boolean submit = true;
    // template end ---8<-----------8<---

} Main // template start ---8<-----------8<---
	FastScanner sc = new FastScanner(System.in); sc new FastScanner(System.in) static PrintWriter out; out final double TEMP = 10; TEMP 10 static final long TL = 5850; TL 5850 static boolean submit = true; submit true public static void main(String[] args) throws IOException {
		out = new PrintWriter(System.out);
		new Main().solve();
		out.flush();
	} main {
		out = new PrintWriter(System.out);
		new Main().solve();
		out.flush();
	} out = new PrintWriter(System.out) out new PrintWriter(System.out) new Main().solve() new Main().solve new Main() out.flush() out.flush out String[] args args void solve() {
		int X = sc.nextInt();
		boolean[] expo = new boolean[X+1];

		expo[1] = true;
		for (int b=2;b<=X;b++) {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		}
		for (int i=X; i>=0;i--){
			if (expo[i]) {
				out.println(i);
				return;
			}
		}



	} solve {
		int X = sc.nextInt();
		boolean[] expo = new boolean[X+1];

		expo[1] = true;
		for (int b=2;b<=X;b++) {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		}
		for (int i=X; i>=0;i--){
			if (expo[i]) {
				out.println(i);
				return;
			}
		}



	} int X = sc.nextInt(); X sc.nextInt() sc.nextInt sc boolean[] expo = new boolean[X+1]; expo new boolean[X+1] X+1 X 1 expo[1] = true expo[1] expo 1 true for (int b=2;b<=X;b++) {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		} int b=2; int b=2; b 2 b<=X b X b++ b++ b {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		} {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		} int v = b*b; v b*b b b while(v<=X) {
				expo[v] = true;
				v *= b;
			} v<=X v X {
				expo[v] = true;
				v *= b;
			} expo[v] = true expo[v] expo v true v *= b v b for (int i=X; i>=0;i--){
			if (expo[i]) {
				out.println(i);
				return;
			}
		} int i=X; int i=X; i X i>=0 i 0 i-- i-- i {
			if (expo[i]) {
				out.println(i);
				return;
			}
		} {
			if (expo[i]) {
				out.println(i);
				return;
			}
		} if (expo[i]) {
				out.println(i);
				return;
			} expo[i] expo i {
				out.println(i);
				return;
			} out.println(i) out.println out i return; ss FastScanner {
		private final InputStream in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		FastScanner(InputStream in) {
			this.in = in;
		}

		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		}

		private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		}

		public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}

		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}
	} FastScanner private final InputStream in; in private final byte[] buffer = new byte[1024]; buffer new byte[1024] 1024 private int ptr = 0; ptr 0 private int buflen = 0; buflen 0 FastScanner(InputStream in) {
			this.in = in;
		} FastScanner {
			this.in = in;
		} this.in = in this.in this this.in in InputStream in in private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		} hasNextByte {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		} if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			} ptr < buflen ptr buflen {
				return true;
			} return true; true {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			} ptr = 0 ptr 0 try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				} catch (IOException e) {
					e.printStackTrace();
				} IOException e {
					e.printStackTrace();
				} e.printStackTrace() e.printStackTrace e {
					buflen = in.read(buffer);
				} buflen = in.read(buffer) buflen in.read(buffer) in.read in buffer if (buflen <= 0) {
					return false;
				} buflen <= 0 buflen 0 {
					return false;
				} return false; false return true; true private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		} readByte {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		} if (hasNextByte())
				return buffer[ptr++];
			else
				return -1; hasNextByte() hasNextByte return buffer[ptr++]; buffer[ptr++] buffer ptr++ ptr return -1; -1 1 private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		} isPrintableChar {
			return 33 <= c && c <= 126;
		} return 33 <= c && c <= 126; 33 <= c && c <= 126 33 <= c 33 c c <= 126 c 126 int c c public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		} hasNext {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		} while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++; hasNextByte() && !isPrintableChar(buffer[ptr]) hasNextByte() hasNextByte !isPrintableChar(buffer[ptr]) isPrintableChar(buffer[ptr]) isPrintableChar buffer[ptr] buffer ptr ptr++ ptr return hasNextByte(); hasNextByte() hasNextByte public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		} next {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		} if (!hasNext())
				throw new NoSuchElementException(); !hasNext() hasNext() hasNext throw new NoSuchElementException(); new NoSuchElementException() StringBuilder sb = new StringBuilder(); sb new StringBuilder() int b = readByte(); b readByte() readByte while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			} isPrintableChar(b) isPrintableChar b {
				sb.appendCodePoint(b);
				b = readByte();
			} sb.appendCodePoint(b) sb.appendCodePoint sb b b = readByte() b readByte() readByte return sb.toString(); sb.toString() sb.toString sb public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		} nextLong {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		} if (!hasNext())
				throw new NoSuchElementException(); !hasNext() hasNext() hasNext throw new NoSuchElementException(); new NoSuchElementException() long n = 0; n 0 boolean minus = false; minus false int b = readByte(); b readByte() readByte if (b == '-') {
				minus = true;
				b = readByte();
			} b == '-' b '-' {
				minus = true;
				b = readByte();
			} minus = true minus true b = readByte() b readByte() readByte if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			} b < '0' || '9' < b b < '0' b '0' '9' < b '9' b {
				throw new NumberFormatException();
			} throw new NumberFormatException(); new NumberFormatException() while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			} true {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			} if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				} '0' <= b && b <= '9' '0' <= b '0' b b <= '9' b '9' {
					n *= 10;
					n += b - '0';
				} n *= 10 n 10 n += b - '0' n b - '0' b '0' if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				} b == -1 || !isPrintableChar(b) b == -1 b -1 1 !isPrintableChar(b) isPrintableChar(b) isPrintableChar b {
					return minus ? -n : n;
				} return minus ? -n : n; minus ? -n : n minus -n n n {
					throw new NumberFormatException();
				} throw new NumberFormatException(); new NumberFormatException() b = readByte() b readByte() readByte public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		} nextInt {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		} long nl = nextLong(); nl nextLong() nextLong if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException(); nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE nl < Integer.MIN_VALUE nl Integer.MIN_VALUE Integer Integer.MIN_VALUE nl > Integer.MAX_VALUE nl Integer.MAX_VALUE Integer Integer.MAX_VALUE throw new NumberFormatException(); new NumberFormatException() return (int) nl; (int) nl public double nextDouble() {
			return Double.parseDouble(next());
		} nextDouble {
			return Double.parseDouble(next());
		} return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next class Random {
		private long seed;
		private final long multiplier = 0x5DEECE66DL, addend = 0xBL, mask = (1L << 48) - 1;
		int bits, val;

		Random(long seed) {
			this.seed = seed;
		}

		int nextInt(int n) {
			do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0);
			return val;
		}

		double nextDouble() {
			return nextInt(10000000) / 10000000.0;
		}
	} Random private long seed; seed private final long multiplier = 0x5DEECE66DL multiplier 0x5DEECE66DL addend = 0xBL addend 0xBL mask = (1L << 48) - 1; mask (1L << 48) - 1 (1L << 48) 1L 48 1 int bits bits val; val Random(long seed) {
			this.seed = seed;
		} Random {
			this.seed = seed;
		} this.seed = seed this.seed this this.seed seed long seed seed int nextInt(int n) {
			do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0);
			return val;
		} nextInt {
			do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0);
			return val;
		} do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0); bits - val + (n - 1) < 0 bits - val + (n - 1) bits - val bits val (n - 1) n 1 0 {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17) bits (int) ((seed = (seed * multiplier + addend) & mask) >>> 17) (seed = (seed * multiplier + addend) & mask) seed (seed * multiplier + addend) & mask (seed * multiplier + addend) seed * multiplier seed multiplier addend mask 17 val = bits % n val bits % n bits n return val; val int n n double nextDouble() {
			return nextInt(10000000) / 10000000.0;
		} nextDouble {
			return nextInt(10000000) / 10000000.0;
		} return nextInt(10000000) / 10000000.0; nextInt(10000000) / 10000000.0 nextInt(10000000) nextInt 10000000 10000000.0 public class Main {
    // template start ---8<-----------8<---
	FastScanner sc = new FastScanner(System.in);
	static PrintWriter out;

	public static void main(String[] args) throws IOException {
		out = new PrintWriter(System.out);
		new Main().solve();
		out.flush();
	}
	// template end ---8<-----------8<---

	void solve() {
		int X = sc.nextInt();
		boolean[] expo = new boolean[X+1];

		expo[1] = true;
		for (int b=2;b<=X;b++) {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		}
		for (int i=X; i>=0;i--){
			if (expo[i]) {
				out.println(i);
				return;
			}
		}



	}

    // template start ---8<-----------8<---
	class FastScanner {
		private final InputStream in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		FastScanner(InputStream in) {
			this.in = in;
		}

		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		}

		private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		}

		public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}

		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}
	}

	class Random {
		private long seed;
		private final long multiplier = 0x5DEECE66DL, addend = 0xBL, mask = (1L << 48) - 1;
		int bits, val;

		Random(long seed) {
			this.seed = seed;
		}

		int nextInt(int n) {
			do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0);
			return val;
		}

		double nextDouble() {
			return nextInt(10000000) / 10000000.0;
		}
	}

	final double TEMP = 10;
	static final long TL = 5850;
	static boolean submit = true;
    // template end ---8<-----------8<---

} public class Main {
    // template start ---8<-----------8<---
	FastScanner sc = new FastScanner(System.in);
	static PrintWriter out;

	public static void main(String[] args) throws IOException {
		out = new PrintWriter(System.out);
		new Main().solve();
		out.flush();
	}
	// template end ---8<-----------8<---

	void solve() {
		int X = sc.nextInt();
		boolean[] expo = new boolean[X+1];

		expo[1] = true;
		for (int b=2;b<=X;b++) {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		}
		for (int i=X; i>=0;i--){
			if (expo[i]) {
				out.println(i);
				return;
			}
		}



	}

    // template start ---8<-----------8<---
	class FastScanner {
		private final InputStream in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		FastScanner(InputStream in) {
			this.in = in;
		}

		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		}

		private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		}

		public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}

		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}
	}

	class Random {
		private long seed;
		private final long multiplier = 0x5DEECE66DL, addend = 0xBL, mask = (1L << 48) - 1;
		int bits, val;

		Random(long seed) {
			this.seed = seed;
		}

		int nextInt(int n) {
			do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0);
			return val;
		}

		double nextDouble() {
			return nextInt(10000000) / 10000000.0;
		}
	}

	final double TEMP = 10;
	static final long TL = 5850;
	static boolean submit = true;
    // template end ---8<-----------8<---

} Main
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.NoSuchElementException;

public class Main {
    // template start ---8<-----------8<---
	FastScanner sc = new FastScanner(System.in);
	static PrintWriter out;

	public static void main(String[] args) throws IOException {
		out = new PrintWriter(System.out);
		new Main().solve();
		out.flush();
	}
	// template end ---8<-----------8<---

	void solve() {
		int X = sc.nextInt();
		boolean[] expo = new boolean[X+1];

		expo[1] = true;
		for (int b=2;b<=X;b++) {
			int v = b*b;
			while(v<=X) {
				expo[v] = true;
				v *= b;
			}
		}
		for (int i=X; i>=0;i--){
			if (expo[i]) {
				out.println(i);
				return;
			}
		}



	}

    // template start ---8<-----------8<---
	class FastScanner {
		private final InputStream in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		FastScanner(InputStream in) {
			this.in = in;
		}

		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		}

		private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		}

		public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}

		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}
	}

	class Random {
		private long seed;
		private final long multiplier = 0x5DEECE66DL, addend = 0xBL, mask = (1L << 48) - 1;
		int bits, val;

		Random(long seed) {
			this.seed = seed;
		}

		int nextInt(int n) {
			do {
				bits = (int) ((seed = (seed * multiplier + addend) & mask) >>> 17);
				val = bits % n;
			} while (bits - val + (n - 1) < 0);
			return val;
		}

		double nextDouble() {
			return nextInt(10000000) / 10000000.0;
		}
	}

	final double TEMP = 10;
	static final long TL = 5850;
	static boolean submit = true;
    // template end ---8<-----------8<---

}

