#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<<a+b;
    } else{
        cout<<n;
    }
}
/**************************************************************
	Problem: 1734
	User: wengsihan
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/