#include <bits/stdc++.h>
int main() {
  int x, y, x1, y1, r;
  scanf("%d %d %d %d %d", &r, &x, &y, &x1, &y1);
  double d = pow(pow(x - x1, 2) + pow(y - y1, 2), 0.5) / (2 * r);
  int n = d;
  if (d > n) n++;
  printf("%d", n);
  return 0;
}
