1112. Sum of Multiples

Your Job

Find the sum of all multiples of n below m

Keep in Mind

• n and m are natural numbers (positive integers)
• m is excluded from the multiples

Examples

sumMul(2, 9)   ==> 2 + 4 + 6 + 8 = 20
sumMul(3, 13)  ==> 3 + 6 + 9 + 12 = 30
sumMul(4, 123) ==> 4 + 8 + 12 + ... = 1860
sumMul(4, -7)  ==> "INVALID"

Solution:

def invalid_value(func):
    def wrapper(n, m):
        return (n<1 or m<1) and "INVALID" or func(n, m)
    return wrapper

@invalid_value
def sum_mul(n, m):
    return sum(range(0, m, n))