#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, a, b, c, d, r;
  cin >> r >> a >> b >> c >> d;
  double x = sqrt((c - a) * (c - a) + (d - b) * (d - b)), y;
  y = x / (2.0 * r);
  cout << ceil(y);
}
