F0,F1,N=map(int,input().split())
#print(F0,F1,N)
if N==0:print(F0)
elif N==1:print(F1)
elif N==2:print(F0^F1)
else:
    for i in range(2,N+1):
        F=F0^F1
        F0,F1=F1,F
    print(F)