编写函数，求出所有符合下列条件的三位正整数：分别乘以 3、4、5、6、7 后得 到的整数的各位数字之和都相等

def find_num():
    for num in range(100, 1000):
        num3 = num * 3
        num4 = num * 4
        num5 = num * 5
        num6 = num * 6
        num7 = num * 7
        if sum(map(int, str(num))) == sum(map(int, str(num3))) == sum(map(int, str(num4))) == sum(map(int, str(num5))) == sum(map(int, str(num6))) == sum(map(int, str(num7))):
            print(num)

find_num() # 输出：142, 285, 428, 571, 714, 857