51nod 1718 Cos的多项式

用x=π/3带入可得。。。。

详细证明方式：Tabris_的博客

//#include<bits/stdc++.h>#include<stdio.h>#include<cstring>#include<cmath>#include<iostream>using namespace std;int main(){long long n;while(~scanf("%lld",&n)){n%=6;if(n==0)printf("2\n");else if(n==1||n==5)printf("1\n");else if(n==2||n==4)printf("-1\n");else if(n==3)printf("-2\n");}}