#include <bits/stdc++.h>
using namespace std;
signed main() {
  long long r, x1, y1, xf, yf;
  cin >> r >> x1 >> y1 >> xf >> yf;
  double d = sqrt((yf - y1) * (yf - y1) + (xf - x1) * (xf - x1));
  cout << (long long)ceil(d / (r * 2)) << '\n';
}
