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


int main() {
    int a,b,c,k;

    scanf("%d %d %d %d",&a ,&b,&k,&c);

    int i;
    long long int sum = 2;
    for (i = 1; i < k; i++){
        sum =(sum <<1 )% 1000000007;
        //printf("Sum %d : %lld\n", i,sum);

    }

    long int pocet;
    pocet = sum * k / 2 % 1000000007;


    if (a ==b )
    {   printf("%d", k);
    }
    else if (c == a || c == b) {
        printf("%ld", pocet);
    }
    else{
        printf("0");
    }
    return 0;
}