def add(a, b):
    c = []
    carry = 0
    n = max(len(a), len(b))
    for i in range(n):
        sum_val = carry
        if i < len(a):
            sum_val += a[i]
        if i < len(b):
            sum_val += b[i]
        c.append(sum_val % 10)
        _______________
    if carry != 0:
        c.append(carry)
    return c