#include <bits/stdc++.h>
using namespace std;
int main() {
  int T;
  T = 1;
  for (int tc = 1; tc <= T; tc++) {
    long long r, ax, ay, bx, by;
    cin >> r >> ax >> ay >> bx >> by;
    long long otisq = (ax - bx) * (ax - bx) + (ay - by) * (ay - by);
    double oti = sqrt(otisq);
    cout << ceil(oti / (2 * r)) << '\n';
  }
}
