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

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