#include <stdio.h>
#include <stdlib.h>

int main()
{
    int cons = 1000000007,a,b,k,c;
    long double count = 0;
    scanf("%d %d %d %d", &a, &b, &k, &c);

    if (a==c || b==c){
        count = pow(2,k-1)*k;
    }
    else{
        count = 0;
    }
    long double help = fmodl(count,cons);
    printf("%.0Lf", help);

    return 0;
}