Simple match calculator

#include <iostream>
#include <iomanip>
#include <stdlib.h>

// Match calculator by Goran

using namespace std;

int main()
{
    int firstNumber, secondNumber;
    float sum;
    string answer, option;

    do{
    cout << "What operation do you want to use ?\n- Addition\n- Subtraction\n- Multiplication\n- Division\n\n";

    // Getting answer from user.

    cin >> answer;

    while(!(answer == "A" || answer == "Addition" || answer == "S" || answer == "Subtraction" || answer == "M" || answer == "Multiplication" || answer == "D" || answer == "Division")){
        cin >> answer;
    }

    // Entering numbers:

    cout << "\nEnter first number: ";
    cin >> firstNumber;

    cout << "Enter second number: ";
    cin >> secondNumber;

    // Operations.

    if(answer == "A" || answer == "Addition"){
        sum = firstNumber + secondNumber;
        cout << "\nResult: " << firstNumber << " + " << secondNumber << " = " << sum << endl;
    }else if(answer == "S" || answer == "Subtraction"){
        sum = firstNumber - secondNumber;
        cout << "\nResult: " << firstNumber << " - " << secondNumber << " = " << sum << endl;
    }else if(answer == "M" || answer == "Multiplication"){
        sum = firstNumber * secondNumber;
        cout << "\nResult: " << firstNumber << " * " << secondNumber << " = " << sum << endl;
    }else if(answer == "D" || answer == "Division"){
        sum = (float)firstNumber / (float)secondNumber; // Changing integer to floats.
        cout << "\nResult: " << firstNumber << " / " << secondNumber << " = " << sum << endl;
    }

    cout << "\nCalculate something else (Yes or No): ";
    cin >> option;

    if(option == "Yes" || option == "Y"){
        system("cls"); // Clears console from text.
    }

    }while(option == "Yes" || option == "Y");

    return 0;
}