# 해당 함수를 완성해주세요
def sol(a, b):
    c = []
    if len(a) == len(b[0]):
        for i in range(len(a)):
            c.append([0]*len(b[0]))
        for i in range(len(c)):
            for j in range(len(c[i])):
                for k in range(len(a[i])):
                    c[i][j] += a[i][k] * b[k][j]
        return c
    else:
        return -1