def reduce_monomial(mono):
    result = {}
    for [k, v] in mono:
        result[k] = (result.get(k, 0) + v)
    return list(result.items())
def reduce_monomial(mono):
    result = {}
    for [k, v] in mono:
        result[k] = (result.get(k, 0) + v)
    return list(result.items())