p,q,r,K=map(int,input().split())




dp={}
for i in range(10):
    for j in range(10):
        for k in range(10):
            dp.setdefault((i,j,k),[0]*64)
            dp[(i,j,k)][0]=((i+j+k)%10,i,j)


for i in range(63):
    for j in range(10):
        for k in range(10):
            for l in range(10):
                dp[((l+j+k)%10,j,k)][i+1]=dp[dp[((j+k+l)%10,j,k)][i]][i]




s=(p%10,q%10,k%10)


for i in range(64):
    if K&(1<<i):
        s=dp[s][i]
print(s[0])