var a,b,c,d:longint;
begin
read(a);
b:=a mod 10;
c:=a div 10;
d:=b*10+c;
if d>a then write(d)
       else write(a);
       end.
/**************************************************************
	Problem: 1625
	User: admin
	Language: Pascal
	Result: Wrong Answer
****************************************************************/