#include <iostream>

#define ll long long int

using namespace std;

int main()
{
	ll a, b, k, c;
	cin >> a >> b >> k >> c;
	if (c != a && c != b)
	{
		cout << "0\n";
		return 0;
	}
	if (a == b)
	{
		cout << k << "\n";
		return 0;
	}
	ll prod = k;
	for (int i = 0; i < k - 1; i++)
	{
		prod *= 2;
		prod %= 1000000007;
	}
	cout << prod << "\n";
	return 0;
}