#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2, i, j, ans = 0;
  double d;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  d = sqrt(((x2 - x1) * (x2 - x1)) + ((y2 - y1) * (y2 - y1)));
  ans = ceil(d / (r * 2));
  cout << ans;
  return 0;
}
