mod = 1000000007 eps = 10**-9 def main(): import sys input = sys.stdin.readline p, q, r, K = map(int, input().split()) p %= 10 q %= 10 r %= 10 K -= 3 X = [p, q, r] seen = [-1] * 1001 pqr = p*100 + q * 10 + r PQR = [pqr] seen[pqr] = 0 while True: X.append((X[-1] + X[-2] + X[-3])%10) pqr_new = X[-3] * 100 + X[-2] * 10 + X[-1] if seen[pqr_new] == -1: seen[pqr_new] = seen[pqr] + 1 pqr = pqr_new PQR.append(pqr) else: L = seen[pqr] + 1 pqr = pqr_new break s = (K - seen[pqr] + L)%L t = seen[pqr] + s print(PQR[t]%10) #print(X) #print(PQR) #print(len(PQR), L) if __name__ == '__main__': main()