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[(j,k,l)][i+1]=dp[dp[(j,k,l)][i]][i]

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

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

print(s[2])