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