#include <iostream>
signed main() {
double x, z;
std::cout << "x=";
std::cin >> x;
z = (2.0 * x + 4.0) / (21.0 * 5.0);
std::cout << "z=" << z;
return 0;
}
#include <iostream>
signed main() {
double x, z;
std::cout << "x=";
std::cin >> x;
z = (2.0 * x + 4.0) / (21.0 * 5.0);
std::cout << "z=" << z;
return 0;
}