import sys
sys.setrecursionlimit(10**6)
f0,f1,n=map(int,input().split())
f={0:f0,1:f1}
def  cal(x):
    if x == 1:return f1
    elif x == 0:return f0
    if x in f:return f[x]
    else:f[x] = cal(x-1)^cal(x-2)
    return f[x]

print(cal(n))