#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x2, y2, x1, y1;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  float d = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
  cout << ceil(d / (2 * r));
  return 0;
}
