#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, gx, gy;
  cin >> r >> x >> y >> gx >> gy;
  double d = sqrt((gx - x) * (gx - x) + (gy - y) * (gy - y));
  cout << ceil(d / (2 * r)) << endl;
  return 0;
}
