#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, xx, yy;
  double dis, val, frac, ing;
  scanf("%d %d %d %d %d", &r, &x, &y, &xx, &yy);
  dis = sqrt(pow(x - xx, 2) + pow(y - yy, 2));
  val = dis / (2.0 * r);
  frac = modf(val, &ing);
  if (frac > 0.0)
    printf("%.0lf\n", val + 1);
  else
    printf("%.0lf\n", val);
  return 0;
}
