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