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