#include <iostream>
#include <exception>
#include <cmath>
#include <sstream>
#include <string>
#include <stddef.h>
using namespace std;

string itos(double i);
int findperfectsquare (double);

int main()
{
        int const endinput(10000);
        try {
                double number(0);
                while (number != endinput) {
                        cout << "Input a number \n";
                        cout << "10000 to end\n";

                        cin >> number;
                        if (number == endinput)
                                break;

                        if (number <= 0)
                                throw exception();
                        number -= 1;
                        int result(0);
                        result = findperfectsquare(number);
                        cout << "The square root of the largest perfect square less than this number is " << result << '\n';
                }
        }

        catch (...) {
                cerr << "***An exception was thrown***\n";
        }
}

int findperfectsquare (double mynumber)
{
        do {
                double numberroot = sqrt(mynumber);
                string myno = itos(numberroot);

                for (size_t i(0); i <= myno.size(); ++i) {
                        if (myno[i] == '.') {
                                mynumber -= 1;
                        } else {
                                return numberroot;
                        }
                }
        } while (true);

}

string itos(double i)
{
        stringstream s;
        s << i;
        return s.str();
}