#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1;
  scanf("%lf %lf %lf %lf %lf", &r, &x, &y, &x1, &y1);
  double dis = sqrt(((x1 - x) * (x1 - x)) + ((y1 - y) * (y1 - y)));
  dis = dis / (r * 2.0);
  cout << ceil(dis) << endl;
  return 0;
}
