package barrels;

import java.util.Scanner;

public class Barrels {

    public static void main(String[] args) {
        // write your code here
        Scanner scanner = new Scanner(System.in);
        int num1 = scanner.nextInt();
        int num2 = scanner.nextInt();
        int length = scanner.nextInt();
        int interested = scanner.nextInt();
        if(interested != num1 && interested != num2)
        {
            System.out.println(0);
            return;
        }
        long res = 1;
        for (int i = 0; i < length; i++) {
            res = res * 2;
            res = res % 1000000007;
        }
        res = (res * length ) % 1000000007;
        res = res / 2;
        System.out.println(res);
    }
}