#include <stdio.h>

typedef unsigned long long Integer;

int main(void)
{
    Integer f0, f1, N;
    scanf("%llu %llu %llu", &f0, &f1, &N);
    Integer a[3] = {f0, f1, f0 ^ f1};
    printf("%llu\n", a[N%3]);
    return 0;
}