#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, a, b, c, d;
  cin >> r >> a >> b >> c >> d;
  double x = (a - c) * (a - c) + (d - b) * (d - b);
  x = sqrt(x);
  double ans = ceil(x / (2 * r));
  printf("%d", (int)ans);
}
