#include <stdio.h>
#include <stdint.h>

typedef int64_t i64;
typedef uint64_t u64;

int main() {
    u64 f0, f1, n;
    scanf("%lu %lu %lu", &f0, &f1, &n);
    u64 a[3] = {f0, f1, f0 ^ f1};
    printf("%lu\n", a[n%3]);
    return 0;
}