#include <iostream>
#include <string>
#include <cmath>
#include <cstdlib>
#include <windows.h>
#include <time.h>
#include <fstream>
#include <algorithm>
#include <stdio.h>
#include <vector>
#define NN 1000000007
#define N 100003
#define ull unsigned long long
#define ll long long
#define lf double
using namespace std;
int main(){
    int i,j,r,x0,y0,x1,y1,rez;
    long double d;
    cin>>r>>x0>>y0>>x1>>y1;
    x0-=x1;
    y0-=y1;
    d=sqrt((long double)x0*x0+y0*y0);
    rez=ceil(d/(2*r));
    cout<<rez;
}
