154369620 I need help to figure out why this solution gave TLE. Thanks!

In problem C of Educational Codeforces Round 114 I was using accumulate function to calculate sum of the elements in an array which IDK why messed up my solution and giving the sum of array larger than actual which eventually caused WA and when the sum calculted in o(n) it accepted the submission

here is accepted submission 129428522 here is WA submission 129427890

is there any limit on using accumulate or anything else?