#include <stdio.h>

int main() {

    int A, B, K, C;
    unsigned int i;

    // 211602592

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

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

    // unsigned long long int *mocnina = (unsigned long long int *) malloc(sizeof(unsigned long long int) * K);
    unsigned long long int mocnina = 1;

    mocnina = 2;

    for (i = 0; i < K - 2 /*((K - 1))*/; i++) {
        mocnina = mocnina % 1000000007;
        mocnina <<= 1;
    }

    if (C == B && B == A) {
        printf("%d\n", (int) (((2 * mocnina) * K) % 1000000007));
    } else {
        printf("%d\n", (int) (((mocnina * K)) % 1000000007));
    }

    return 0;
}