import bisect,collections,copy,heapq,itertools,math,string,sys,queue,time,random
input = lambda: sys.stdin.readline().rstrip()
def I(): return input()
def IS(): return input().split()
def II(): return int(input())
def IIS(): return map(int,input().split())
def LIIS(): return list(map(int,input().split()))
def Base_n_to_10(X,n):
    out = 0
    for i in range(1,len(str(X))+1):
        out += int(X[-i])*(n**(i-1))
    return out#int out
def Base_10_to_n(X, n):
    if (X//n):
        return Base_10_to_n(X//n, n)+str(X%n)
    return str(X%n)
INF=10**18
MOD=10**9+7
sys.setrecursionlimit(10**8)
##############################################################################
p,q,r,k=IIS()
li=[0 for i in range(10**5)]
li[0]=p%10
li[1]=q%10
li[2]=r%10
i=3
while True:
    li[i]=(li[i-1]+li[i-2]+li[i-3])%10
    if li[i]==r%10 and li[i-1]==q%10 and li[i-2]==p%10:
        #i-2こ
        break
    i+=1
li=li[:i-2]
print(li[k%(i-2)-1])