findM.py

def solution(U, L, C):
    # write your code in Python 3.6
    if U + L != sum(C):
        return "IMPOSSIBLE"
    res = [[0 for j in range(len(C))] for i in range(2)]
    for i, s in enumerate(C):
        if s == 2:
            if U == 0 or L == 0:
                return "IMPOSSIBLE"
            res[0][i] = 1
            res[1][i] = 1
            U -= 1
            L -= 1
        elif s == 1:
            if U > L:
                res[0][i] = 1
                U -= 1
            else:
                res[1][i] = 1
                L -= 1

    return "".join(map(str, res[0])) + "," + "".join(map(str, res[1]))