#include <stdio.h>

long power(int k,int c);

int main()
{
	int a,b,c,k;
	scanf("%d %d %d %d",&a,&b,&k,&c);
	if(c!=a&&c!=b)
		printf("0\n");
	else
	{
	long res;
	res=(power(2,k)*k)/2;
	res=res%1000000007;
	
	printf("%ld\n",res);
	}
	return 0;			
}

long power(int c,int k)
{
	int i;
	long r=1;
	for(i=0;i<k;i++)
		r=r*c;
	return r;
}