#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, a1, a2, b1, b2, c;
  cin >> r >> a1 >> b1 >> a2 >> b2;
  double d;
  d = sqrt((a1 - a2) * (a1 - a2) + (b1 - b2) * (b1 - b2));
  cout << ceil(d / (2 * r));
}
