#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, p, q;
  cin >> r >> x >> y >> p >> q;
  int a = x - p;
  int b = y - q;
  double d = sqrt(pow(a, 2) + pow(b, 2));
  printf("%0.0lf", ceil(d / (2 * r)));
}
