
import java.util.*;
import java.io.*;
import java.math.*;
public class aprail152
{
    static class InputReader {
        private InputStream stream;
        private byte[] inbuf = new byte[1024];
        private int start= 0;
        private int end = 0;
        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        private int readByte() {
            if (start == -1) throw new UnknownError();
            if (end >= start) {
                end= 0;
                try {
                    start= stream.read(inbuf);
                } catch (IOException e) {
                    throw new UnknownError();
                }
                if (start<= 0) return -1;
            }
            return inbuf[end++];
        }

        private boolean isSpaceChar(int c) {
            return !(c >= 33 && c <= 126);
        }

        private int skip() {
            int b;
            while ((b = readByte()) != -1 && isSpaceChar(b)) ;
            return b;
        }

        public String next() {
            int b = skip();
            StringBuilder sb = new StringBuilder();
            while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != ' ')
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public int nextInt() {
            int num = 0, b;
            boolean minus = false;
            while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')) ;
            if (b == '-') {
                minus = true;
                b = readByte();
            }

            while (true) {
                if (b >= '0' && b <= '9') {
                    num = num * 10 + (b - '0');
                } else {
                    return minus ? -num : num;
                }
                b = readByte();
            }
        }

        public long nextLong() {
            long num = 0;
            int b;
            boolean minus = false;
            while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')) ;
            if (b == '-') {
                minus = true;
                b = readByte();
            }

            while (true) {
                if (b >= '0' && b <= '9') {
                    num = num * 10 + (b - '0');
                } else {
                    return minus ? -num : num;
                }
                b = readByte();
            }
        }
    }
    static class card{
        int up;
        int down;
        public card(int u,int d)
        {
            this.up=u;
            this.down=d;
        }
    }
    static class sort implements Comparator<card>
    {
        public int compare(card o1,card o2)
        {
            if(o1.down!=o2.down)
                return (o1.down-o2.down)*-1;
            else
                return (o1.up-o2.up)*-1;
        }
    }
    static void shuffle(long a[])
    {
        List<Long> l=new ArrayList<>();
        for(int i=0;i<a.length;i++)
            l.add(a[i]);
        Collections.shuffle(l);
        for(int i=0;i<a.length;i++)
            a[i]=l.get(i);
    }

    static int gcd(int a,int b)
    {
        if(b==0)
            return a;
        else
            return gcd(b,a%b);
    }
    static long ans;
    public static void main(String args[])
    {
        InputReader sc=new InputReader(System.in);
        long r=sc.nextLong();
        long x1=sc.nextLong();
        long y1=sc.nextLong();
        long x2=sc.nextLong();
        long y2=sc.nextLong();
        System.out.println((long)Math.ceil(Math.hypot(x2-x1,y2-y1)/(2*r)));
    }
}

