#include <iostream>
#include <cmath>
using namespace std;
const unsigned prime = 1000000007;

unsigned myPow(int x, int n)
{
    unsigned out=1;
    for(unsigned i = 0; i < n; i++)
    {
        out=(out*x)%prime;
    }
    return out;

}

int main()
{
    unsigned a,b,k,c, out = 0;
    cin>>a>>b>>k>>c;
    if(a==c || b==c)
    {
        out = (myPow(2, k-1)*k)%prime;
    }
    cout<<out<<endl;

    return 0;
}