Guard , thief and money Puzzle in C++

#include <iostream>
using namespace std;
int main()
{
    string _input ;
    bool _protected=false , money_reached , valid=false ;
    again :
    cout<<"Enter the input : ";
    cin>>_input;
    for(int i=0;i<_input.length();i++)
    {
        if(_input[i]=='$')
        {
            valid=true;
            break;
        }
    }
    if(!valid)
    {
        cout<<"Input must contain $\n";
        goto again ;
    }
    for(int i=0;i<_input.length();i++)
    {
        if(_input[i]=='T')
        {
            _protected = false ;
        }
        else if(_input[i]=='G')
        {
            _protected = true ;
        }
        if(money_reached&&(_input[i]=='T'||_input[i]=='G'))
        {
            break ;
        }
        else if(_input[i]=='$')
        {
            if(_protected)
            {
                cout<<"Protected from left";
            }
            else
            {
                cout<<"Not Protected from left";
            }
            _protected = false ;
            money_reached = true;
        }
    }
    cout<<endl;
    if(_protected)
    {
        cout<<"Protected from right";
    }
    else
    {
        cout<<"Not Protected from right";
    }
}