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