def exponent(base, exp):
    result = 1
    for i in range(1, exp + 1):
        result *= base

    return result


input_line = input()
a, b, k, c = input_line.split()
a = int(a)
b = int(b)
k = int(k)
c = int(c)
res = 0

if a == c or b == c:
    if a != b:
        res = (exponent(2, k) * k) / 2
    elif a == b:
        res = k

print(int(res) % 1000000007)