两个整数的最大公约数（欧几里得算法）

unsigned int Gcd(unsigned int M, unsigned int N) {
    unsigned int Rem;
    if(M >= N) {
        while(N > 0) {
            Rem = M % N;
            M = N;
            N = Rem;
        }
        return M;
    } else {
        int T = M;
        M = N;
        N = T;
        Gcd(M,N);
    }
}