1) Slow algorithm O(K*(K+1)/2) : brute force. AC : 0.2 !
-> Find the profit with each number of horn and hoof (horn + hoof <= k).

2) Fast algorithm O(K*2) : caching the optimal number of horns and hoof. AC : 0.031 !
Find :
   +     The optimal number of horns <= k (A)
   +     The optimal number of hoof <= k - num of horns (B)
=>    result = A + B;

2) More Fast algorithm O(K) : caching the optimal number of horn or hoof. AC : 0.031 !
Caching the number of hoof.
-> For each number of horn
   + The optimal number of hoof = 0 ... k - optimal num of horn.

first algorithm could be optimized to AC in 0.046 :)