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)