#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  double r, x, y, x0, y0;
  int res = 0;
  cin >> r >> x >> y >> x0 >> y0;
  double dist = sqrt((x - x0) * (x - x0) + (y - y0) * (y - y0));
  cout << ceil(dist / (2 * r)) << endl;
}
