#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a,b;
	cin>>n;
	a=n%10*10;
	b=n/10%10*1;
	if(n>a+b){
		cout<<n;
	}else{
		cout<<a+b;
	}
	
} 
/**************************************************************
	Problem: 1625
	User: linzihang
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/