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