#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x0, y0, x1, y1, ju;
  scanf("%lf %lf %lf %lf %lf", &r, &x0, &y0, &x1, &y1);
  ju = sqrt((x0 - x1) * (x0 - x1) + (y0 - y1) * (y0 - y1));
  double d = 2 * r;
  int jie = ju / d;
  if (jie * d < ju) jie++;
  printf("%d\n", jie);
  return 0;
}
