line = input()
line = list(map(int, line.split()))

if(line[0] != line[3] and line[1] != line[3]):
    print(0)

elif line[0]==line[3] and line[1] == line[3]:
    print(line[2])

else:
    print((line[2] * (2 ** (line[2] - 1))) % 1000000007)