#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long long dx = abs(x2 - x1);
  long long dy = abs(y2 - y1);
  cout << ceil(sqrt(dx * dx + dy * dy) / (2.0 * r)) << endl;
  return 0;
}
