class UnusualAdd {
public:
    int addAB(int A, int B) {
        // write code here
        if(A==0)
            return B;
        
        if(B==0)
            return A;
        
        int tem=0;//代表进位位
        do{
            tem=A&B;
            A=A^B;
            B=tem<<1;
        }while(B!=0);
        return A;
    }
};