#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);
        sum = sum  % 1000000007;
    }
    //printf("mocnina %lld\n", sum);
    long long int pocet = 0;
    sum = (sum >> 1);
    //printf("Pred %lld\n", sum);
    sum = sum * k;
    //printf("Po %lld\n", sum);
    pocet = sum %  1000000007;
    //printf("Modulo %lld\n", pocet);

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