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