Undo and Redo in C++

#include <iostream>
using namespace std;
int main()
{
    string current,past="",next;
    int undo_redo;
    cout<<"Enter a text"<<endl;
    cin>>current;
    next=current;
    again:
    cout<<"The current text : "<<current<<endl<<endl;
    cout<<endl<<"If you want to undo , enter 0 ... don't want , Enter 1 ... want to redo , Enter 2 ... want to enter a new text , Enter 3"<<endl;
    cin>>undo_redo;
    if(undo_redo==0)
    {
        next=current;
        current=past;
    }
    else if(undo_redo==2)
    {
        past=current;
        current=next;
    }
    else if(undo_redo==3)
    {
        past=current;
        cout<<"Enter the new text"<<endl;
        cin>>current;
        next=current;
    }
    goto again;
}