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

x=[[0]*3 for _ in range(3)]
x[0][0]=1
x[0][1]=1
x[0][2]=1
x[1][0]=1
x[2][1]=1

mod=10
def mul(a,b):
    n=len(a)
    res=[[0]*n for i in range(n)]
    for i in range(n):
        for j in range(n):
            for k in range(n):
                res[i][j]+=a[i][k]*b[k][j]
                res[i][j]%=mod
    return res
def mpow(a,n):
    if n==1:return a
    res=mpow(a,n//2)
    res=mul(res,res)
    if n%2==1:
        res=mul(res,a)
    return res

x=mpow(x,k-3)

ans=r*x[0][0]+q*x[0][1]+p*x[0][2]
ans%=10
print(ans)