1) int d; std::cin >> d;
const int pi = 3.14;
double L = pi * d;
std::cout << L << std::endl;</p>
2) int R; std::cin >> R;
const int pi = 3.14;
double L = 2*pi*R;
double S = pi * R * R;
std::cout << L << S << std::endl;</p>
3) int a,b; std::cin >> a >> b;
int c = (a+b) / 2;
std::cout << c << std::endl;</p>