C++ switch while infinite loop issue

I’m a total beginner at C++ and I’m trying to make a program which displays train schedule by selecting routes from the menu. I also want to make it possible to choose multiple options and quit manually. The issue is: every input creates an infinite loop.

#include <iostream>
#include <iomanip>
#include <locale>
using namespace std;

struct {
    string Route;
    string depTime;
    string travelTime;
    string endDestTime;
} Schedule1, Schedule2, Schedule3;

int main()
{
    setlocale(LC_ALL, "RUSSIAN");
    int routeNum = 3;
    bool quit = false;
    
    Schedule1.Route = "Ярославль--Москва"; //route 
    Schedule1.depTime = "12.06.2023, 13:00"; //departure time
    Schedule1.travelTime = "4 часа"; //travel time
    Schedule1.endDestTime = "12.06.2023, 17:00"; //destination time
    
    Schedule2.Route = "Ярославль--Санкт-Петербург";
    Schedule2.depTime = "12.06.2023, 16:00";
    Schedule2.travelTime = "10 часов";
    Schedule2.endDestTime = "13.06.2023, 02:00";
    
    Schedule3.Route = "Ярославль--Екатеринбург";
    Schedule3.depTime = "12.06.2023, 12:00";
    Schedule3.travelTime = "20 часов";
    Schedule3.endDestTime = "13.06.2023, 08:00";
  
    
    //train routes to choose from
    cout<<"|----------------Расписание поездов-----------------| \n\n";
    cout<<"Город отправления:     Город прибытия: \n";
    cout<<"(1)  Ярославль         Москва \n";
    cout<<"(2)  Ярославль         Санкт-Петербург \n";
    cout<<"(3)  Ярославль         Екатеринбург \n";
    cout<<"(4)  Завершить" << endl;
    cout<<"Выберите номер маршрута: ";
    cin >> routeNum;

    do
    {
    switch (routeNum)
    {
        case 1:
        cout << "Маршрут: " << Schedule1.Route << " " << endl;
        cout << "Время отправления: " << Schedule1.depTime << " " << endl;
        cout << "Время в прибытия: " <<  Schedule1.endDestTime << " " <<endl;
        cout << "Время в пути: " << Schedule1.travelTime << " " <<endl;
        cout<<endl;
        break;
        
        case 2:
        cout << "Маршрут: " << Schedule2.Route << " " << endl;
        cout << "Время отправления: " << Schedule2.depTime << " " << endl;
        cout << "Время в прибытия: " <<  Schedule2.endDestTime << " " <<endl;
        cout << "Время в пути: " << Schedule2.travelTime << " " <<endl;
        cout<<endl;
        break;
        
        case 3:
        cout << "Маршрут: " << Schedule3.Route << " " << endl;
        cout << "Время отправления: " << Schedule3.depTime << " " << endl;
        cout << "Время в прибытия: " <<  Schedule3.endDestTime << " " <<endl;
        cout << "Время в пути: " << Schedule3.travelTime << " " <<endl;
        cout<<endl;
        break;
        
        case 4:
        quit = true; //quit program
        break;
        
        default:
        cout << "Выберите существующий номер маршрута"; //if input is invalid
    } 
    }
    while(!quit);

    
    return 0;
}

I know same issue has been brought before but I still can’t figure out what I’m missing here. Any help would be greatly appreciated.

>Solution :

At least this statement

cin >> routeNum;

should be within the do-while loop as for example

do
{
cin >> routeNum;

switch (routeNum)
{
//...

Otherwise the variable routeNum is not being changed within the loop. As a result you have an infinite loop.