【Light】[1213]Fantasy of a Summation

#include<stdio.h>
int f(int x,int n,int mod) {
int res=1;
while(n>0) {
if(n&1)
res=(res*x)%mod;
x=(x*x)%mod;
n>>=1;
}
return res;
}
int main() {
int T,kase=0;
scanf("%d",&T);
while(T--) {
int n,K,MOD;;
scanf("%d %d %d",&n,&K,&MOD);
int sum=0;
for(int i=0; i<n; i++) {
int t;
scanf("%d",&t);
sum=sum+t%MOD;
}
sum%=MOD;
int k=K%MOD;
int res=f(n,K-1,MOD);
printf("Case %d: ",++kase);
printf("%d\n",(long long)((long long)sum*(long long)k*(long long)res)%MOD);
}
return 0;
}