#Given 3 int values, a b c, return their sum. If one of the values is 13 then
# it does not count towards the sum and values to its right do not count.
# So for example, if b is 13, then both b and c do not count.

def lucky_sum(a, b, c):
    sum = a + b + c
    if a == 13:
        sum = 0
    elif b == 13:
        sum = a
    elif c == 13:
        sum = a + b
    return sum


print(lucky_sum(1, 2, 3))  # 6
print(lucky_sum(1, 2, 13)) # 3
print(lucky_sum(1, 13, 3)) # 1
