快速幂 + 推公式
#include<iostream>
#include<math.h>
using namespace std;
typedef long long LL;
int qmi(LL k,LL p)
{
long long res = 1;
long long a = 10;
while(k)
{
if(k&1) res = res * a %p;
k>>=1;
a = a*a%p;
}
return res;
}
int main()
{
LL n,m,k,x;
scanf("%lld%lld%lld%lld",&n,&m,&k,&x);
LL temp = (x % n + (qmi(k,n)* m %n )%n)%n;
cout<<temp<<endl;
}