Functions Problem

[Ruined Embrace]

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
    string lastName;
    double number, target, parkingSticker;
    const double SENTINEL = 000000;
    
    cout << "Please enter a parking sticker number (enter 000000 to exit): " << endl;
    cin >> target;
    
    while (target != SENTINEL)
    {
          string findName(int foundName)
          {
             bool found = false;
             string foundName = "NOT FOUND";
          
             ifstream input("HWK5.txt");
             if (input.is_open())
             {

                 input >> lastName >> parkingSticker;             
                 while (! input.eof() && !found)
                 {
                     if (target == parkingSticker)
                     {
                         foundName = lastName;
                         found = true;
                     }
                   input >> lastName >> parkingSticker;                     
                 }
             }
          input.close();
          return foundName;
          }
    }
    if (foundName != "NOT FOUND")            
       cout << "The parking sticker number belongs to " << lastName << endl;
    else
       cout << "This parking sticker is not on file. Try again." << endl;
              
    system("pause");
    return 0;
}

Still many problems.