import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


def matrix_multiplication_mod(A,B,p):
    l = len(A)
    m = len(B)
    n = len(B[0])
    C = [[0]*n for _ in range(l)]
    for i in range(l):
        for j in range(n):
            C[i][j] = sum((A[i][k]*B[k][j]) % p for k in range(m)) % p
    return C


def matrix_power_mod(A,n,p):
    l = len(A)
    C = [[0] * l for _ in range(l)]
    for i in range(l):
        C[i][i] = 1
    while n > 0:
        if n % 2 == 1:
            C = matrix_multiplication_mod(C,A,p)
        A = matrix_multiplication_mod(A,A,p)
        n >>= 1
    return C


p,q,r,K = MI()
A = [[1,1,1],[1,0,0],[0,1,0]]
X = matrix_power_mod(A,K-3,10)
ans = X[0][0]*r+X[0][1]*q+X[0][2]*p
ans %= 10
print(ans)