#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double a = hypot(x1 - x, y1 - y);
  int k = int(a);
  if (a > k) k += 1;
  r *= 2;
  if (k % r == 0)
    cout << k / r;
  else
    cout << k / r + 1;
  return 0;
}
