#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  r *= 2;
  long long lim = (a - x) * (a - x) + (b - y) * (b - y);
  double dis = sqrt((double)(a - x) * (a - x) + (double)(b - y) * (b - y));
  long long ans = (int)(dis / r) - 1;
  if (ans < 0) ans = 0;
  while (true) {
    long long tmp = ans * r;
    if (tmp * tmp >= lim) {
      cout << ans << endl;
      return 0;
    }
    ans++;
  }
  return 0;
}
