I'm writing a code that takes a quantity input from the user for five items in a company

My problem is when the user enters a decimal value for the quantity of one of the items, the program ends automatically. What I need it to do, on the other hand, is to display a message letting the user know that they made a mistake and give them the option to try again.

I've tried using the cin.fail() function with no luck whatsoever.

 cout<< "\nEnter number of Whizbangs: ";
 cin>> WhizbangsAmt;
 //This screens out all the negative numbers
 while(true)
 {
     if(WhizbangsAmt < 0)
     {
         cout<< "Number is negative!\n";
         cout<< "Enter number of Whizbangs: ";
         cin>> WhizbangsAmt;
     }
     else
     {
         break;
     }
 }