#include <bits/stdc++.h>
using namespace std;
const int N = int(3e6);
int a, b, x, y, r;
int main() {
  cin >> r >> x >> y >> a >> b;
  double k = sqrt(1ll * (x - a) * (x - a) + 1ll * (y - b) * (y - b));
  cout << int(k / (2 * r) + 0.999999999999999);
  return 0;
}
