import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.MathContext;

public class Main {
    static int modulo = 1000000007;

    public static void main(String args[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        String[] numbers = line.split(" ");
        int firstDigit = Integer.parseInt(numbers[0]);
        int secondDigit = Integer.parseInt(numbers[1]);
        int length =  Integer.parseInt(numbers[2]);
        int searchedNumber = Integer.parseInt(numbers[3]);

        if (searchedNumber != firstDigit && searchedNumber != secondDigit) {
            System.out.println("0");
        } else {
            if (firstDigit != secondDigit) {
                
                double result = (Math.pow(2, length) * length) / 2;


                System.out.println((int)result);
            } else {
                System.out.println(length % modulo);
            }
        }


    }

}