#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  r *= 2;
  cout << ceil(sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)) / r);
}
