f(a,b){return b?(b&1)*a^f(a*2,b/2):0;}
 
 
 
void test_case(int a, int b, int ab) {
    int t = f(a,b);
 
    if (t != ab) {
        printf("Error! Test case %d @ %d = %d, but f(%d, %d) = %d\n", a, b, ab, a, b, t);
    }
    else {
        printf("%d @ %d = %d\n", a, b, t);
    }
}
 
int main() {
    test_case(0, 1, 0);
    test_case(1, 2, 2);
    test_case(9, 0, 0);
    test_case(6, 1, 6);
    test_case(3, 3, 5);
    test_case(2, 5, 10);
    test_case(7, 9, 63);
    test_case(13, 11, 127);
    test_case(5, 17, 85);
    test_case(14, 13, 70);
    test_case(19, 1, 19);
    test_case(63, 63, 1365);
    return 0;
}

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