#include <bits/stdc++.h>
int main() {
  int r, x, y, x1, y1, i, j, k, d;
  scanf("%d %d %d %d %d", &r, &x, &y, &x1, &y1);
  d = pow((x - x1), 2) + pow((y - y1), 2);
  i = ceil(sqrt(d) / (2 * r));
  printf("%d\n", i);
}
