#include <iostream>

unsigned long long pw(unsigned int n){
	unsigned long long r = 1;
	for(int i=0; i<n; i++){
		r = r * 2;
		r %= 1000000007;
	}
	return n * r % 1000000007 / 2;
}

int main(){
	int a=0,b=0,k=0,c=0;
	std::cin>>a>>b>>k>>c;
	unsigned long long res = pw(k);
	if(c != a && c != b)
		std::cout << 0 << std::endl;
	else
		std::cout << (res) << std::endl;
}