#include <bits/stdc++.h>
using namespace std;
int r, x, y, x2, y2;
int main() {
  cin >> r >> x >> y >> x2 >> y2;
  r *= 2;
  double res =
      (double)(sqrt((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y))) / (double)(r);
  printf("%d", (int)(ceil(res)));
}
