F0, F1, N = map(int, input().split())

if N == 0:
    print(F0)
    exit()
if N == 1:
    print(F1)
    exit()
    
A = F0 ^ F1
B = F1 ^ A
C = A ^ B

if N % 3 == 2:
    print(A)
elif N % 3 == 0:
    print(B)
else:
    print(C)