#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, x1, y1, d;
  while (cin >> r >> x >> y >> x1 >> y1) {
    double a = pow((x - x1), 2) + pow((y - y1), 2);
    d = sqrt(a);
    cout << ceil(d / (2 * r)) << endl;
  }
  return 0;
}
