#include <stdio.h>

unsigned long long power(int k);

int main()
{
	int a,b,c,k;
	scanf("%d %d %d %d",&a,&b,&k,&c);
	if((c!=a&&c!=b)||k==0)
		printf("0\n");
	else
	{
		if(a==b)
			printf("%d\n",k);
		else
		{
			unsigned long long res;
			res=power(k);
			
			printf("%lld\n",res);
		}
	}
	return 0;			
}

unsigned long long power(int k)
{
	int i;
	unsigned long long r=1;
	for(i=0;i<k-1;i++)
	{
		r=(r*2)%1000000007;
			
	}
	r=(k*r)%1000000007;
	return r;
}