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

void f0();
void f1();
void f2();
void f3();

int main()
{
	void (*const a[])() = {
		f0,   //or &f0, with explicit "address of" operator
		f1,
		f2,
		f3
	};
	const size_t n = sizeof a / sizeof a[0];

	size_t i;   //uninitialized variable
	cin >> i;

	if (i >= n) {
		cerr << "input " << i << " must be in the range 0 to " << n - 1
			<< " inclusive\n";
		return EXIT_FAILURE;
	}

	a[i]();   //or (*a[i])() with explicit dereferencing operator
	return EXIT_SUCCESS;
}