#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 * 2);
        sum = sum % 1000000007;
    }
    //printf("mocnina %lld\n", sum);
    long long int pocet = 0;
    pocet = sum >> 1;
    pocet = pocet *k  % 1000000007;
    //pocet = ((pocet >> 1) * k)% 1000000007;

    /*if (a == b && a == c) {
        printf("%d", k);
    } else if (c == a || c == b) {
        printf("%lld", pocet);
    } else {
        printf("0");
    }
    */
    if ((c == a || c == b) && a != b){
        printf("%lld", pocet);
    }
    else if (c != a && c != b ){
        printf("0");
    }
    else if (a == b && a == c){
        printf("%d", k);
    }

    return 0;
}