if __name__ == "__main__":

    line = input()
    split = line.split()
    
    a = int(split[0])
    b = int(split[1])
    k = int(split[2])
    c = int(split[3])

    variations = 2**k

    res = variations * k

    res /= 1 + (a != b)

    res = res if c in (a, b) else 0

    print(int(res % (1000 * 1000 * 1000 + 7)))