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

int main() {
    long int a, b, k, c, vys=1, i=1;

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

    for(i=1; i<k; i++) {
        vys *= 2;
        if (vys > 1000000007)
            vys %= 1000000007;
    }

    if (c==a && c==b)
        printf("%d", (int)(2*k*vys)%1000000007);
    else if (c==a || c==b)
        printf("%d", (int)(k*vys)%1000000007);
    else
        printf("%d", 0);


    return 0;
}