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