import java.math.BigInteger;
import java.util.Scanner;

public class Barrels {

    public static int A;
    public static int B;
    public static int L;
    public static int F;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (sc.hasNextInt()) {
            A = sc.nextInt();
            B = sc.nextInt();

            L = sc.nextInt();
            F = sc.nextInt();

            if (A == B && A == F) {
                System.out.println(L);
            } else if (F == A || F == B) {
                BigInteger sum = new BigInteger("0");
                for (long i = 0; i <= L; i++) {
                    BigInteger m = factorial(i).multiply(factorial(L - i));
                    BigInteger c = factorial(L);
                    BigInteger z = c.divide(m);
                    sum = sum.add(z.multiply(new BigInteger(String.valueOf(i)))).mod(new BigInteger("1000000007"));
                }
                System.out.println(sum);
            } else {
                System.out.println(0);
            }
        }
    }

    public static BigInteger factorial(long n) {
        if (n == 0) {
            return new BigInteger("1");
        }

        BigInteger bi = new BigInteger(String.valueOf(n));
        for (long i = n - 1; i > 0; i--) {
            bi = bi.multiply(new BigInteger(String.valueOf(i)));
        }

        return bi;
    }

}