from freq_stack import FreqStack


def main(input_1, input_2):
    result = []
    obj = FreqStack()
    result.append(None)

    for i in range(1, len(input_1)):
        if input_1[i] == "push()":
            res = obj.push(input_2[i])
            result.append(res)
        elif input_1[i] == "pop()":
            res = obj.pop()
            result.append(res)
    
    return result