소스 코드 제출

#1280

# a,b=map(int,input().split())

# s=0

# for i in range(a,b+1):

# if (i)%2==0 :

# s=s-i

# print('-',i,sep='',end='')

# else :

# s=s+i

# print('+',i,sep='',end='')

#

# print('=',s,end='',sep='')

# 1270

# a=int(input())

# s=0

# for i in range(1,a+1):

# if i%10==1:

# s=s+1

#

# print(s)

a,b,c,n=map(int,input().split())

s=a

for i in range(n-1):

s=s*b+c

print(s)