NEFU 115

刚开始，做了水题

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;

int main(){
	int n;
	int a31,a32,a41,a42,a121,a122,ans3,ans4,ans12;
	while(scanf("%d",&n)!=EOF){
		a31=a32=a41=a42=a121=a122=1;
		for(int i=3;i<=n;i++){
			ans3=(a31+a32)%3;
			ans4=(a41+a42)%4;
			ans12=(a121+a122)%12;
			a31=a32; a32=ans3;
			a41=a42; a42=ans4;
			a121=a122; a122=ans12;
		}
		if(ans12==0)
		printf("YES\n");
		else if(ans4==0)
		printf("4\n");
		else if(ans3==0)
		printf("3\n");
		else printf("NO\n");
	}
	return 0;
}