#include <iostream>
#include <fstream>
#include <set>
#include <algorithm>
using namespace std;
set<char> c;
void Add(set<char>& s)
{
    char a;
    ifstream file ("example.txt",ios::in);
    while(!file.eof())
    {
        file>>a;
        if(s.insert(a).second)
            cout<<"Inserted "<<a<<endl;
        else
            cout<<"Already exists"<<endl;
    }
    cout<<"Insertion complete!"<<endl;
    system("pause");
    system("cls");
}
void Print(set<char>& s)
{
    set<char>::iterator it;
    for(it=s.begin();it!=s.end();it++)
        cout<<*it<<" ";
}
set<char> alphabet;
set<char> v;
set<char>::iterator it;
void AddAlpha(set<char>& s)
{
    char letter='a';
    for(letter='a';letter<122;letter++)
    {
        s.insert(letter);
    }
}
int main()
{
    AddAlpha(alphabet);
    Add(c);
    Print(c);
    cout<<endl;
    it=set_difference(c.begin(),c.end(),alphabet.begin(),alphabet.end(),v.begin());
    cout<<"There is "<<v.size()<<" letters not used!"<<endl;
    cout<<"\nThey are: "<<endl;
    Print(v);
    cout<<endl;
    system("pause");
    return 0;
}