def subset_sum(L, k, n) :
    if (n == 0):
        return True
    if (k == 0 and n != 0):
        return False
    if (k > len(L)):
        return False
    if (L[k - 1] > n) :
        return subset_sum(L, k - 1, n);

    return subset_sum(L, k-1, n) or subset_sum(L, k-1, n-L[k-1])


print(subset_sum([2,3,4], 2, 5))
print(subset_sum([2,3,4], 3, 9))
print(subset_sum([2,3,4], 2, 8))
print(subset_sum([2,3,4], 12, 8))
print(subset_sum([2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18], 5, 100))