inp = raw_input("")

cisielocka = inp.split(" ")
a = int(cisielocka[0])
b = int(cisielocka[1])
k = int(cisielocka[2])
c = int(cisielocka[3])
vysledocek=0

if(a == c or b == c):
	vysledocek = ((2**(k-1) * k))%1000000007

print(vysledocek)