Negative number check

The code on lines 44-53 is suppose to display a message when the user enter a negative number, however, when a correct positive number is entered the message is display again.

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#include<iostream>
#include<cctype>
using namespace std;

int main()
{
   
 char carType;
 int A, B, C;
 char keepgoing;
 char condition; 
 double miles, per_miles,upgrade;
 double days, per_days,new_char;
 double price, fees, charges,discount, new_charges;


   
 do
 {
   
  do
  { 
    cout<<"Which car are you shopping for? (enter A, B, C)?"<<endl;
    cin>>carType;
      
    }while (carType != 'A' && carType != 'B' && carType != 'C' );
      
      

    cout<<"What condition? (S, O, or, P)"<<endl;
    cin>>condition;
     
    if ((condition !='S') || (condition !='O') || (condition !='P'));
     
    
    else
      cout<<"Please enter the correct response"<<endl;
    
    
    
    cout<<"How many miles?"<<endl;
    cin>>miles;
    
 do 
  {
   
  cout<<"How many days?"<<endl;
  cin>>days;
  
  cout<<"You enter a negative number,please try again."<<endl;
  
  
 }while (days < 0);
    
         cout.setf(ios::fixed);
         cout.setf(ios::showpoint);
         cout.precision(2);

      
      
         switch(carType)
      {
       
         case 'A':
         
         per_miles = miles * 0.10;
         per_days = days * 29.95;
         price = per_miles + per_days;
         
                  
         break;
         
         case 'B':
         
         per_miles = miles * 0.15;
         per_days = days * 35.95;
         price = per_miles + per_days;
         
         
              
         break;
         
         case 'C':
         
          per_miles = miles * 0.20;
         per_days = days * 39.95;
         price = per_miles + per_days;
         
                           
               
         break;
         
         default:
         cout<<"You entered an incorrect car choice"<<endl;
         }
         
         if(condition =='O')
         {
            fees = price * 0.10;
            price = price - fees;
         
         cout<<"The charges are?"<<price<<endl;
         
         
         
         }
         else if (condition == 'P')
         {
            fees = price * 0.10;
            price = price + fees;
                      
         cout<<"The charges are?"<<price<<endl;
         
        
         
         
         }
         else
         {
         cout<<"The charges are?"<<price<<endl;
         }
         
                    
               if (condition =='S')
               {
               fees = price * 0.10;
               new_charges = price + fees;
               discount = new_charges * 0.05;
               upgrade = new_charges - discount;
               
               cout<<"You may upgrade for a total cost of $"<<upgrade<<endl;
              }            
             else if(condition =='O')
             {
               discount = price * 0.05;
               upgrade = price - discount;
               
               cout<<"You may upgrade for a total cost of $"<<upgrade<<endl;
            }
            else
            {          
           cout<<"There are upgrades avialble"<<endl;
           
           }
         
               
         cout<<"Do you want another one (y/n)?"<< endl;
         cin>>keepgoing;
         
         }while (keepgoing == 'Y' || keepgoing == 'y');
         
         cout<<"Thank you for using this program. Goodbye."<<endl;
         }
         
                                        
You don't actually check the sign of the number in the 44-53 fragment.
Try to reproduce your problem with a simpler program
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#include <iostream>
using namespace std;

int main(){
   double days; //┬┐double?
   do
   {
   
      cout<<"How many days?"<<endl;
      cin>>days;
  
      cout<<"You enter a negative number,please try again."<<endl;
   }while (days < 0);
}
Also note, indentation.

If you follow that snip you should realize that you print the message of `negative number' before checking it.
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