f0, f1, n = list(map(int, input().split(' ')))

if n ==0:
    print(f0)
elif n == 1:
    print(f1)
else:
    l = len(bin(max([f0, f1]))) - 2
    result = 0
    for i in range(0, l):
        a = (f0 >> i) & 1
        b = (f1 >> i) & 1
        d = 0            

        if a == b == 1:
            if n % 3 != 2:
                d = 1
        elif a == 1:
            if n % 3 != 1:
                d = 1
        elif b == 1:
            if n % 3 != 0:
                d = 1
                
        result += d * 2 ** i
    print(result)