#include <iostream>
#include <cmath>
using namespace std;
int main()
{
int D, day = 0, s = 0;
cin >> D;
while (s != D){
day++;
s = s + day * pow(-1, day + 1);
}
cout << day;
return 0;
}
s = s + day * pow(-1, day + 1);
1. pow很慢,不要用
2. pow改掉後雖然能AC (0.7s),但還是慢,其實答案是有規律的,不需要用到迴圈,你再觀察看看