#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, cx, cy, x, y;
  cin >> r >> cx >> cy >> x >> y;
  float res = (cx - x) * (cx - x) + (cy - y) * (cy - y);
  res = sqrt(res);
  cout << ceil(res / (2.0 * r)) << endl;
  return 0;
}
