import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")
writef = lambda x: print("{:.12f}".format(x))


p,q,r,K = list(map(int, input().split()))
K -= 1
l = [p%10,q%10,r%10]
for i in range(10**6):
    l.append((l[-3]+l[-2]+l[-1])%10)
    if (l[0], l[1], l[2]) == (l[-3], l[-2], l[-1]):
        break
n = len(l) # (0,1,2) = (n-3, n-2, n-1)
k = K % (n-3)
ans = l[k]
print(ans)