p,q,r,k = map(int,input().split())
dp = [0]*1005
dp[1] = p%10
dp[2] = q%10
dp[3] = r%10
s = dp[1]*100+dp[2]*10+dp[3]
c = 0
for i in range(4,1005):
	dp[i] = dp[i-1]+dp[i-2]+dp[i-3]
	dp[i] %= 10
	if dp[i-2]*100+dp[i-1]*10+dp[i]==s:
		c = i-3
		break
print(dp[k%c] if k%c!=0 else dp[c])