import java.util.*;

public class Codeforces {
    static Scanner sc;
    public static void main(String[] args){
        sc = new Scanner(System.in);
        int t = 1;

        while(t-- > 0){
            solve();
        }

        sc.close();
    }

    private static void solve() {

        long r = sc.nextLong();
        long x = sc.nextLong();
        long y = sc.nextLong();
        long x1 = sc.nextLong();
        long y1 = sc.nextLong();

        long count = (long) Math.ceil(Math.sqrt(Math.abs(x1-x)*Math.abs(x1-x) + Math.abs(y1-y)*Math.abs(y1-y)));
        long res = 0;
        long temp = 2*r;
        if(count % temp == 0)
            res = count/temp;
        else
            res = count/temp + 1;
        System.out.println(res);
    }



    public static void sort2dArray (long[][] arr) {
        Arrays.sort(arr, (a, b) -> {
            if (a[1] == b[1])
                return (int) (a[0] - b[0]);
            return (int) (a[1] - b[1]);
        });
    }



}

