MPROD-problem lunchtime

I was unable to solve this problem during the contest and after i was going through the submissions.so,i found this code which is coded by @dreamoon4 who is ranked 1 in this contest but i am unable to understand his code.Can anyone explain me what does he mean from the following statement .

REP(i,pn){
int tmp=max(sum[i]%2,ma[i]2-sum[i]);
REP(j,tmp)an=(an
pp[i])%MOD;
}

http://www.codechef.com/viewsolution/3793782

i checked his result it is absolutely true but how can one arrive at such result.

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