题解 | 加减乘除

while True:
    try:

        def res(a, b, op):
            if op == '+':
                return a+b
            elif op == '-':
                return a-b
            elif op == '*':
                return a*b
            elif op == '/':
                if b == 0:
                    return 'error'
                else:
                    return int(a/b)
            elif op == '%':
                if b == 0:
                    return 'error'
                else:
                    return a%b
        def mul(n):
            if n == 1:
                return 1
            return n * mul(n - 1)

        s = input().split()
        if len(s) == 3:
            a = s[0]
            b = s[2]
            op = s[1]
            a = int(a)
            b = int(b)
            print(res(a, b, op))
        else:
            print(mul(int(s[0])))
    except:
        break