#include <iostream>

using namespace std;

int main()
{
	setlocale(LC_ALL, "rus");
	int A;
	cout << ("Введите A = ");
	while (!(cin >> A) || (cin.peek() != '\n'))
	{
		cin.clear();
		while (cin.get() != '\n');
		cout << ("Введите целое число: ");
	}
	if (A < 2) {
		cout << "F(A) = " << A;
	}
	else if (A >= 2 && A <= 3) {
		cout << "F(A) = " << 2;
	}
	else {
		cout << "F(A) = " << - A + 5;
	}
}