#!/usr/bin/env python3
import sys

def main():
    # N = int(input())
    # N, K = map(int,input().split())
    # A = list(map(int,input().split()))
    f0, f1, K = map(int,input().split())
    # A = list(map(int,input().split()))
    A = [f0, f1]
    c = 0
    for aa in A:
        c ^= aa
    A.append(c)
    print(A[K % len(A)])

if __name__ == '__main__':
    main()