#include <stdio.h>

int main() {

    int A, B, K, C;
    unsigned int i;
    unsigned long long int mocnina = 1;

    scanf("%d %d %d %d", &A, &B, &K, &C);

    if (C != A && C != B) {
        printf("0\n");

        return 0;
    }

    for (i = 0; i < K; i++)
        mocnina = (mocnina * 2) % 1000000007;


    printf("%d\n", (int) (mocnina * K) / 2);

    return 0;
}