#include <bits/stdc++.h>
using namespace std;
int main() {
  double a, b, r, x1, x2, y1, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double ans = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  r *= 2;
  double v = ans / r - (int)ans / r;
  if (v != 0) {
    cout << (int)ans / r + 1 << endl;
  } else {
    cout << (int)ans / r << endl;
  }
  return 0;
}
