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

# print(a.split(' '))

sum = 0

if c == a or c == b:
    temp = 2
    for i in range(1, k-1):
        temp *= 2
        temp = temp % 1000000007
    sum = (temp * k )  % 1000000007

print(int(sum))

exit(0)