#include <fstream>
using namespace std;
ifstream cin("divk.in");
ofstream cout("divk.out");
long long n,k,a,c,v[500005],s,i,j,d,nr,b[500005],x;
int main()
{cin>>n>>k>>a>>c;
for (i=1; i<=n; i++)
{
    cin>>v[i];
    b[i]=v[i]+b[i-1];
    if (b[i]%k==0) nr++;
}
x=nr*(c-a);
cout<<x;
    return 0;
}