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

int main()
{
    int cons = 1000000007,a,b,k,c;
    long double count = 0;
    scanf("%d %d %d %d", &a, &b, &k, &c);
    long double help;

    if(a==b){
        count = k;
        help = count;
    }
    else if (a==c || b==c){
        count = pow(2,k-1)*k;
        help = fmodl(count,cons);
    }
    else{
        count = 0;
        help = count;
    }
    printf("%.0Lf", help);

    return 0;
}