#include <bits/stdc++.h>
using namespace std;
int main() {
  long double r, x, y, a, b, distance;
  cin >> r >> x >> y >> a >> b;
  distance = sqrt(pow(abs(x - a), 2) + pow(abs(y - b), 2));
  cout << fixed << setprecision(0) << ceil(ceil(distance) / (2 * r));
  return 0;
}
