#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x, y, a, b;
  double d;
  cin >> r >> x >> y >> a >> b;
  d = sqrt((x - a) * (x - a) + (y - b) * (y - b));
  cout << ceil(d / (r * 2));
}
