#include <bits/stdc++.h>
int main(void) {
  long long int r, x, y, x1, y1, i, d;
  scanf("%lld%lld%lld%lld%lld", &r, &x, &y, &x1, &y1);
  d = sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
  if (d % (2 * r) != 0)
    printf("%lld", d / (2 * r - 1) + 1);
  else
    printf("%lld", d / (2 * r - 1));
  return 0;
}
