My damned solution keep giving WA on test 6 with C11. I tested on big numbers and every corner case (yes, it works with 1 1 -> '0', yes, it gives '-1' on 3 6, etc..)
Suggestions? What's in test 6?
The exact same algorithm in python gives AC.. (and it's not a bignum issue, I tested the C version with 43 and 10**9)
