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

    return res

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

if a != b:
    res = (exponent(2, k) * k) / 2
else:
    res = k

print(int(res) % 1000000007)