import sys

for ln in sys.stdin:
    ln = ln.strip()
    x = ln.split(" ")
    a = int(x[0])
    b = int(x[1])
    k = int(x[2])
    c = int(x[3])

    M=1000000007

    if k == 0:
        print(0)
        continue

    if a == b:
        if a == c:
            print(k%M)
        else:
            print(0)
    else:
        if a != c and b != c:
            print(0)
        else:
            print((2**(k-1)*k)%M)