disp(' Introduce the ends A and B. Choose them such that A < B');
   A=input('A=');
   B=input('B=');
   Product=f(A)*f(B);
   
   while Product>0
   		disp('There is not root in the given interval');
   		disp(' Choose new values for the ends of the interval');
   		A=input('A=');
   		B=input('B=');
   		Product=f(A)*f(B);
   end; 
      
 % If the product<0 then the choice is correct. We can incorporate this message
   
  disp('The choice of A and B is appropriate to find a root');