#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  long long r, x1, x2, y1, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double s = sqrt((double)((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)));
  cout << (long long)(s / r / 2 + 0.999) << endl;
  return 0;
}
