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