#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    long long a,b,k,c, out = 0;
    cin>>a>>b>>k>>c;
    if(a==c || b==c)
    {
        out = (pow(2, k)*k)/2;
    }
    cout<<out%1000000007<<endl;
    return 0;
}