#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double dist = pow(x1 - x, 2) + pow(y1 - y, 2);
  dist = pow(dist, 0.5);
  cout << ceil(dist / (2 * r)) << '\n';
}
