First of all, I hope you picked an answer before you started coding. This is cheating ;)
Second, when you set amt, you don't take the amount out of the arr[y]. As in, you place a bet, but the money you bet appears out of thin air. arr[y] = arr[y] + amt*2 should not have the *2.
Also, 50 should be 51.
As luck would have it, I coded it myself (after guessing, and getting it terribly wrong). Here's the relevant fragment of my PowerShell code.