#include <iostream>
#include <cmath>




using namespace std;

int main()
{

    int a = 0/*0*/,b = 0/*1*/,k = 0,c = 0, poceta = 0, pocetb = 0, pocetc = 0;
    cin >> a >> b >> k >> c;
    if(!(((a >=1 && a <=9) || (b >=1 && b <=9) ||(c >=1 && c <=9))&& k>=0 && k <=1000)) {
        return 0;
    }
    bool *zahrada = new bool[k];

    for(int i = 0;  i < k; i++){
        zahrada[i] = false;
        poceta++;
    }

    int power_2_k = pow(2,k);

    int iterace =0;

        while(iterace < power_2_k - 1){
        for(int i = 0;  i < k; i++){
        if(c == b){
            if(zahrada[i] == true)
            pocetb++;
        } else if ( c == a) {
         if(zahrada[i] == false)
            pocetb++;
        }

    }

            for(int i = k-1; i >=0; i--){
                if(zahrada[i] == false){
                    zahrada[i] = true;


                    break;
                }

                if(zahrada[i] == true){



                    zahrada[i] = false;
                }
            }

            iterace++;


        }


    int prib = (pocetb + k)%1000000007;
    int pria = pocetb %1000000007;
        if(c ==b)
        cout << prib;
        else if(c == a)
             cout << pria;


    return 0;
}