#include <bits/stdc++.h>
using namespace std;
const int N = 100005;
int main() {
  int n, m, i, j, k, l, t, tl, x, y, p;
  double d, r, ax, ay, bx, by;
  while (~scanf("%lf%lf%lf%lf%lf", &r, &ax, &ay, &bx, &by)) {
    d = (ax - bx) * (ax - bx) + (ay - by) * (ay - by);
    d = sqrt(d);
    r = r * 2;
    t = d / r;
    if (fabs(d - t * r) <= (1e-8))
      printf("%d\n", t);
    else
      printf("%d\n", t + 1);
  }
  return 0;
}
