#include <iostream>
#include <cstdlib>
using namespace std;

void f(int *p, size_t n);	//change first arg to const int *p

int main()
{
	int a[] = {10, 20, 30};
	const size_t n = sizeof a / sizeof a[0];

	f(a, n);

	for (size_t i = 0; i < n; ++i) {
		cout << a[i] << "\n";
	}

	return EXIT_SUCCESS;
}

void f(int *p, size_t n)
{
	for (size_t i = 0; i < n; ++i) {
		cout << p[i] << "\n";
	}

	p[1] = 21;
}