var
 a1,a2,a3,m:WORD;
 b:BOOLEAN;
Begin
 Write('a1= ');
 ReadLn(a1);
 Write('a2= ');
 ReadLn(a2);
 Write('a3= ');
 ReadLn(a3);
 m:=(a1 div 2);
 b:=FALSE;
 Repeat
  b:=((a1 mod m)=0) and
     ((a2 mod m)=0) and
     ((a3 mod m)=0) and
     (m>1);
  DEC(m);
 Until b OR (m=1);
 If b then
  Writeln('The greatest common divisor is ',m)
  else
  Writeln('These numbers have no common divisors');
 ReadLn;
End.