import sys
f = [0] * 3
f[0], f[1], N = map(int, input().split())
if N < 2:
    print(f[N])
    sys.exit()
for i in range(2, N%3):
    f[2] = f[0] ^ f[1]
    f[0], f[1], = f[1], f[2]
print(f[2])