Number 0 .. 100

#include <iostream>
#include <string>

using namespace std;

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


    if (number >0 && number <= 19) {
        switch (number)
        {
        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;

        default:
            break;
        }
    }
    else if (number < 100 && number >= 20) {
        int first_digit = number / 10;
        int second_digit = number % 10;

        switch (first_digit) {
        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 (second_digit) {
        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 < 0 || number > 100) {
        cout << "invalid number";
    }
    if (number == 0) {
        cout << "zero";
    }
    if (number == 100) {
        cout << "one hundred";
    }
    return 0;
}