HNOI 2013 bzoj 3142 数列

/**************************************************************
Problem: 3142
User: Clare
Language: C++
Result: Accepted
Time:0 ms
Memory:1272 kb
****************************************************************/

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <queue>
#include <vector>
using namespace std;

typedef long long ll;

ll n,K,m,P;

ll Quickpow(ll a,ll exp)
{
ll base=a,r=1;
while(exp)
{
if(exp&1)
r=r*base%P;
base=base*base%P;
exp>>=1;
}
return r;
}

int main()
{
scanf("%lld%lld%lld%lld",&n,&K,&m,&P);
n%=P;
ll Ans=n*Quickpow(m,K-1)%P;
ll tmp=(((m*(m+1)/2%P)*Quickpow(m,K-2))%P*(K-1))%P;
Ans=((Ans-tmp)%P+P)%P;
printf("%lld",Ans);
return 0;
}