I have a little bit problem about cin on C++ (Please guide me =w=)

Question

From this code, there are 2 parts, First is the main menu(Function StockSelect) and the second one is submenu(ShowStockMenu).

The problem is I just want it to get out from submenu to the main menu when I typed the alphabet, but this code just skips the 'cin' part of the main menu and jump right to the end of the program (exit the program).

#include<iostream>
#include <fstream>
#include<stdlib.h>

using namespace std;

bool StockSelect(int &stocknum);
int ShowStockMenu();

int main()
{
int stocknum;
while(StockSelect(stocknum))
{
int inqchoice = ShowStockMenu();
switch(inqchoice)
{
case 1:
//PriceDataInquiry(stocknum);
cout<<endl<<"1"<<endl;
break;
case 2:
//GainLossCalculation(stocknum);
cout<<endl<<"2"<<endl;
break;
default:
cout<<">>Invalid number... Going back to menu<<"<<endl<<endl;
cout<<endl<<"--------------------------------------------"<<endl;
break;
}
}
return 0;
}
bool StockSelect(int &stocknum)
{
cout<<"Type number (1-5) to select stock"<<endl;
cout<<" 1. A"<<endl;
cout<<" 2. B"<<endl;
cout<<" 3. C"<<endl;
cout<<" 4. D"<<endl;
cout<<" 5. E"<<endl<<endl;
cout<<"Stock number : ";
double NoDeci;//to remove the case that has decimal
cin>>NoDeci;
cout<<endl;
if(NoDeci==1 || NoDeci==2 || NoDeci==3 || NoDeci==4 || NoDeci==5)
{
stocknum = NoDeci;
return true;
}
cout<<endl<<"Invalid Number!...Quiting";
exit(EXIT_FAILURE);
}
int ShowStockMenu()
{
cout<<"----------------------------"<<endl;
cout<<"Type number 1 or 2 to select"<<endl;
cout<<" 1 : PriceDataInquiry"<<endl;
cout<<" 2 : GainLossCalculation"<<endl<<endl;
cout<<"Enter the number : ";
double NoDeci;
cin>>NoDeci;
cout<<endl;
if(NoDeci==1 || NoDeci==2)
{
return NoDeci;
}
return 0;
}

Answer 1

Alpha5and5 Thank you so much •w•

Answer 2

Alpha5and5 I already tried to fix it by using cin.clear and cin.ignore(numeric_limits<streamsize>::max(),'\n') but I'm not sure whether it is technically right or not(._.)

and here is the link (not the edited one) https://code.sololearn.com/cCTyvdChVj2K/#cpp