Timer for minutes and seconds

#include<iostream>
#include <ctime> // time
#include <thread> // sleep_for
#include <string> // stoi

using namespace std;
using namespace std::this_thread; // sleep_for


// This function takes a string from the console and
// tries to convert it to an integer. If successful, it
// returns the integer. If an exception is thrown, it
// rethrows the exception to the main function.
int validate_input(string input)
{

    // Assume invalid input and validate.
    bool input_is_valid = false;
    int input_int = 0; // String converted to integer.

    while (input_is_valid == false) // While the input is invalid,
    {
        try // Watch for exceptions.
        {
            // convert_input_to_integer throws these exceptions:
            // invalid_argument and out_of_range
            input_int = stoi(input); // Convert input to integer.
            input_is_valid = true; // If no exception, input is valid.
        }
        catch (...) // Catch any exception.
        {
            throw; // Get new input from the calling function.
        }
    }

    return input_int; // Return the input converted to integer.
}

// Wait the requested number of seconds, then
// return to the calling function.
void run_timer(int seconds)
{
    time_t time_start = time(NULL); // Start now.
    // Get the current time and subtract the start
    // time from it. While the difference is less
    // than the requested number of seconds,
    while (time(NULL) - time_start < seconds)
    {
        // Wait one second.
        sleep_for(std::chrono::seconds(1));
    }

    // Return to the calling function.
    return;
}

int main()
{
    string minutes; // User's requested number of minutes.
    int minutes_int = 0; // Minutes converted to an integer.
    string seconds; // User's requested number of seconds.
    int seconds_int = 0; // Seconds converted to an integer.
    int total_seconds = 0; // Total seconds requested.
    const char beep = 7; // A sound to make when the timer is done.
    bool input_is_valid = false; // Assume invalid input and validate.

    cout << "Set the timer.\n"
        "How many minutes? ";
    while (input_is_valid == false) // While the minutes input is invalid,
    {
        try // Watch for exceptions.
        {
            getline(cin, minutes); // Get minutes.
            minutes_int = validate_input(minutes); // Validate input.
            input_is_valid = true; // The input passed validation.
        }
        catch (...) // Catch any exceptions.
        {
            cout << "Number of minutes is invalid. Be sure to enter an integer.\n";
        }
    }

    input_is_valid = false;  // Assume invalid seconds input and validate.
    cout << "How many seconds? ";
    while (input_is_valid == false) // While the seconds input is invalid,
    {
        try // Watch for exceptions.
        {
            getline(cin, seconds); // Get seconds.
            seconds_int = validate_input(seconds); // Validate input.
            input_is_valid = true; // The input passed validation.
        }
        catch (...) // Catch any exceptions.
        {
            cout << "Number of seconds is invalid. Be sure to enter an integer.\n";
        }
    }

    total_seconds = (minutes_int * 60) + seconds_int; // Calculate total seconds requested.
    cout << "Timer will run now ...\n";
    run_timer(total_seconds); // Run the timer.
    cout << beep << '\n'; // Make a sound when time is up.
    cout << "Time is up!\n";

    return 0; // End the program.
}