#include<cstdio>
using namespace std;

void byvalue(int a){
	a = 500;
}

void pass_a_pointer(int *a){
	*a = 500;
}

void byreference(int &a){
	a = 256;
}

void constreference(const int &a){
// a = 357; // Can't do that, we promised not to change it!
}

int main(){
	int a = 10;
	byvalue(a);
	printf("a = %d\n", a);

	pass_a_pointer(&a);
	printf("a = %d\n", a);
	
	byreference(a);
	printf("a = %d\n", a);

	constreference(a);

	return 0;
}