функция exit

#include<iostream>
using namespace std;
int a;
int b;
int value;
char operation;
char quit;
int sum(int,int);
int minu(int,int);
int mult(int,int);
int div(int,int);
int exit(int);
int main()
{
cout<<"Please input value a and b"<<endl;
cin>>a;
cin>>b;
cout<<"What do you want? + - * /"<<endl;
cin>>operation;
if(operation=='+')
    {
        sum(a,b);
        cout<<"a + b = " << value << endl;
        cout<<"Do you want to quit? y/n"<< endl;
        cin>>quit;
        if(quit=='y')
            {
            main();
            }
        else if(quit=='n')
            {
                exit(0);
            }
 
    }
if(operation=='-')
    {
        minu(a,b);
        cout<<"a - b = " << value << endl;
        cout<<"Do you want to quit? y/n"<< endl;
        cin>>quit;
        if(quit=='y')
            {
            main();
            }
        else if(quit=='n')
            {
                exit(0);
            }
    }
if(operation=='*')
    {
        mult(a,b);
        cout<<"a * b = " << value << endl;
        cout<<"Do you want to quit? y/n"<< endl;
        cin>>quit;
        if(quit=='y')
            {
            main();
            }
        else if(quit=='n')
            {
                exit(0);
            }
    }
if(operation=='/')
    {
        div(a,b);
        cout<<"a % b = " << value << endl;
        cout<<"Do you want to quit? y/n"<< endl;
        cin>>quit;
        if(quit=='y')
            {
            main();
            }
        else if(quit=='n')
            {
                exit(0);
            }
    }
return 0;
}
int sum(int,int)
{
value = a + b;
return(value);
}
int minu(int,int)
{
value = a - b;
return(value);
}
int mult(int,int)
{
value = a * b;
return(value);
}
int div(int,int)
{
value = a / b;
return(value);
}

int main()
{
do{
cout<<"Please input value a and b"<<endl;
cin>>a;
cin>>b;
cout<<"What do you want? + - * /"<<endl;
cin>>operation;
if(operation=='+')
    {
       value= sum(a,b);
        cout<<"a + b = " << value << endl;
       
    }
if(operation=='-')
    {
       value= minu(a,b);
        cout<<"a - b = " << value << endl;
 
    }
if(operation=='*')
    {
        value= mult(a,b);
        cout<<"a * b = " << value << endl;
   
    }
if(operation=='/')
    {
        value=div(a,b);
        cout<<"a % b = " << value << endl;
     } 
        cout<<"Do you want to quit? y/n"<< endl;
        cin>>quit;
  }  while(quit='Y' || quit=='y')
return 0;
}