#include <stdio.h>

int main(void)
{
    long F0, F1, N;
    scanf("%ld%ld%ld", &F0, &F1, &N);
    if (N % 3 == 0) printf("%ld", F0);
    else if (N % 3 == 1) printf("%ld", F1);
    else printf("%ld", F0 ^ F1);
    return 0;
}