#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double road = sqrt(((x - x1) * (x - x1)) + ((y - y1) * (y - y1)));
  int a = (road - r) / r;
  cout << (a > 0) ? a : 0;
  return 0;
}
