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