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