main.cpp

#include <iomanip>
#include <iostream>
#include <cmath>

int main() {
  const double pi = 3.14;
  double orderedDiameter;
  int orderedPizzas;
  double substitutionDiameter;  
  double orderedArea;
  double substitutionArea;
  int minSubstitutionPizzas;

  std::cout << "Enter the diameter of the ordered pizza (inches): ";
  std::cin >> orderedDiameter;

  std::cout << "Enter the number of ordered pizzas: ";
  std::cin >> orderedPizzas;

  std::cout << "Enter the diameter of the substitution pizza (inches): ";
  std::cin >> substitutionDiameter;
    
  orderedArea = orderedPizzas * pi * (orderedDiameter / 2.0) * (orderedDiameter / 2.0);
  substitutionArea = pi * (substitutionDiameter / 2.0) * (substitutionDiameter / 2.0);
  minSubstitutionPizzas = std::ceil(orderedArea / substitutionArea);

  std::cout << "Total area ordered: " << orderedArea << " square inches\n";
  std::cout << "Area per substitution pizza: " << substitutionArea << " square inches\n";
  std::cout << "Minimum substitution pizzas needed: " << minSubstitutionPizzas << '\n';

  return 0;
}