20250618

# c=input()
#
# c=int(c)
#
# e=0
#
# for i in range(1,c+1) :
#
#     if i%2==0 :
#
#         e=e+i
#
# print(e)
# c=input()
# c=int(c)
# e=0
# for i in range(1,10) :
#     e=c*i
#     print("%d*%d=%d"%(c,i,e))
# c,d = input().split()
# c=int(c)
# d=int(d)
# if c>d :
#      for i in range(d, c + 1, 1):
#           print(i )
# else :
#      for i in range(c,d+1,1) :
#           print(i )

a, b, c, n = map(int, input().split())
e = 0
e = a
for i in range(n) :
    e=e*b+c
print(e)