#include <bits/stdc++.h>
int main() {
  double r, x, y, x1, y1;
  while (scanf("%lf%lf%lf%lf%lf", &r, &x, &y, &x1, &y1) != EOF) {
    double len = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
    int k = len / (r * 2);
    if ((len - k * r * 2) < 0.000000001)
      printf("%d\n", k);
    else
      printf("%d\n", k + 1);
  }
  return 0;
}
