#include <stdio.h>

long int factorial(long int n) {
    if (n == 0) return 1;
    long int k = n;
    while (k > 1) {
        n = (n * (--k)) % 1000000007;
    }
    return n;
}

int main() {
    int a, b, k, c;
    long int counter = 1;
    scanf("%d %d %d %d", &a, &b, &k, &c);

    if (k == 0) {
        printf("0\n");
        return 0;
    }
    if (c != a && c != b) {
        printf("0\n");
        return 0;
    }
    if (a == c && b == c) {
        printf("%d\n", k);
        return 0;
    }

    for (int j = 1; j < k; ++j) {
        counter = (counter * 2) % 1000000007;
    }

    printf("%ld\n", (counter * k) % 1000000007);
    return 0;
}