Number 0...100 to Text

#include <iostream>
using namespace std;

int main() {
    int number;
    cin >> number;

    if (number >= 0 && number < 20)
    {
        switch (number){
        case 0: cout << "zero" << endl; break;
        case 1: cout << "one" << endl; break;
        case 2: cout << "two" << endl; break;
        case 3: cout << "three" << endl; break;
        case 4: cout << "four" << endl; break;
        case 5: cout << "five" << endl; break;
        case 6: cout << "six" << endl; break;
        case 7: cout << "seven" << endl; break;
        case 8: cout << "eight" << endl; break;
        case 9: cout << "nine" << endl; break;
        case 10: cout << "ten" << endl; break;
        case 11: cout << "eleven" << endl; break;
        case 12: cout << "twelve" << endl; break;
        case 13: cout << "thirteen" << endl; break;
        case 14: cout << "fourteen" << endl; break;
        case 15: cout << "fifteen" << endl; break;
        case 16: cout << "sixteen" << endl; break;
        case 17: cout << "seventeen" << endl; break;
        case 18: cout << "eighteen" << endl; break;
        case 19: cout << "nineteen" << endl; break;
        }
    }
    else if (number >= 20 && number < 100)
    {
        int firstDigit = number / 10;
        int secondDigit = number % 10;

        switch (firstDigit)
        {
        case 2: cout << "twenty "; break;
        case 3: cout << "thirty "; break;
        case 4: cout << "forty "; break;
        case 5: cout << "fifty "; break;
        case 6: cout << "sixty "; break;
        case 7: cout << "seventy "; break;
        case 8: cout << "eighty "; break;
        case 9: cout << "ninety "; break;
        }

        switch (secondDigit)
        {
        case 1: cout << "one" << endl; break;
        case 2: cout << "two" << endl; break;
        case 3: cout << "three" << endl; break;
        case 4: cout << "four" << endl; break;
        case 5: cout << "five" << endl; break;
        case 6: cout << "six" << endl; break;
        case 7: cout << "seven" << endl; break;
        case 8: cout << "eight" << endl; break;
        case 9: cout << "nine" << endl; break;
        }
    }
    else if (number == 100)
    {
        cout << "one hundred" << endl;
    }
    else if (number < 0 || number > 100)
    {
        cout << "invalid number" << endl;
    }
}