【数论】 nefu 702 The minimum square sum

数论这种东西。。。记住结论就好。。。

题目描述。。

Given a prime p (p<10⁸),you are to find min{x²+y²},where x and y belongs to positive integer, so that x²+y²=0 (mod p).

#include <iostream>  
#include <sstream>  
#include <algorithm>  
#include <vector>  
#include <queue>  
#include <stack>  
#include <map>  
#include <set>  
#include <bitset>  
#include <cstdio>  
#include <cstring>  
#include <cstdlib>  
#include <cmath>  
#include <climits>  
#define maxn 1105
#define eps 1e-6 
#define mod 10007 
#define INF 99999999  
#define lowbit(x) (x&(-x))  
#define lson o<<1, L, mid  
#define rson o<<1 | 1, mid+1, R  
typedef long long LL;
using namespace std;

int main(void)
{
	LL p;
	while(scanf("%I64d", &p)!=EOF){
		if(p == 2) printf("%I64d\n", p);
		else if((p-3)%4 == 0) printf("%I64d\n", 2*p*p);
		else printf("%I64d\n", p);
	}
	return 0;
}