#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,g,s;
	cin>>a;
	g=a/1%10; 
	s=a/10;
	g!=s;
	b=g*10+s;
	if(b>a){
		printf("%d",b);
	}if(b<a){
		printf("%d",a);
	}
}
/**************************************************************
	Problem: 1625
	User: sucongyi
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/