(*PROGRAM INF12*);                                
                                                  
  VAR X,Y:INTEGER;                                
                                                  
  FUNCTION GGT(A,B:INTEGER):INTEGER;              
   VAR C:INTEGER;                                 
  BEGIN                                           
   REPEAT                                         
     C:=A MOD B;                                  
     A:=B;B:=C                                    
   UNTIL B=0;                                     
   GGT:=A                                         
  END;                                            
                                                  
 BEGIN                                            
  WRITELN("GGT BERECHNUNG");                      
  WRITELN("··············");                      
  WRITELN("(X,Y>0;X>Y)");                         
  WRITELN("ABBRUCH MIT X=0");                     
  REPEAT                                          
   READLN(X,Y);                                   
   WRITE("X =",X,"Y= ",Y);                        
   IF(X>Y)AND(Y>0) THEN WRITELN(" GGT=",GGT(X,Y)) 
   ELSE WRITELN(" UNZULAESSIGE PARAMETER")        
  UNTIL X=0                                       
 END.