MPROD-problem lunchtime

doubt

#1

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*%2,ma**2-sum*);
REP(j,tmp)an=(anpp)%MOD;
}

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


#2

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