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

print(int(sum))

exit(0)