#include <iostream>
double calculateY(double x) {
return -0.78 * x * x + 10;
}
int main() {
double x;
std::cout << "Enter the value of x: ";
std::cin >> x;
double y = calculateY(x);
std::cout << "The value of the function y = -0.78*x*x + 10 is: " << y << std::endl;
return 0;
}