void byValue(int x) { x = 100; }
void byRef(int& x) { x = 200; }
void byPointer(int* x) { *x = 300; }
int main() {
    int a = 1, b = 2, c = 3;
    byValue(a);
    byRef(b);
    byPointer(&c);
    return 0;
}