UVa - 10364 - Square

What is wrong with my solution for UVa - 10364 - Square ?

Algorithm : Divide the array of integers into 4 subsets, each of them having the same sum. I have used recursive backtracking to check all the possible combination. But for few cases it is showing WA.

Problem : Online Judge

Code : https://hastebin.com/qazanutagi.cpp

Thanks.