#include<iostream>

using namespace std;

long long a, b, k, c, m = 1e9+7;

int main()
{
	cin>>a>>b>>k>>c;
	if(a == b && b == c)
	{
		cout<<k<<endl;
		return 0;
	}
	if(c == a || c == b)
	{
		long long ans = k;
		for(int i = 0; i < k-1; i++)
		{
			ans = (2*ans)%m;
		}
		cout<<ans<<endl;
		return 0;
	}
	cout<<0<<endl;
	return 0;
}