class Solution:
    def addBinary(self, a: str, b: str) -> str:
        tmpa = a
        tmpb = b
        if len(a)>len(b):
            a = tmpb
            b = tmpa
        while len(a) < len(b): a = '0' + a
        print(a, b)
        flag = 0
        indb = len(b) - 1
        rlt = ""
        for inda in range(len(a)-1, -1, -1):
            numa = int(a[inda])
            numb = int(b[indb])
            s = numa + numb + flag
            print(s)
            if s == 3:
                rlt = '1' + rlt
                flag = 1
            if s == 2:
                flag = 1
                rlt = '0' + rlt
            if s == 1: 
                flag = 0
                rlt = '1' + rlt
            if s == 0: 
                flag = 0
                rlt = '0' + rlt
            indb -= 1
            print(f'rlt: {rlt}')
        if flag == 1: rlt = '1' + rlt
        return rlt