#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,y,max;
	scanf("%d",&n);
	y=n/10+n%10*10;
	max=n;
	if (max<y){
		max=y;
		printf("%d\n",max);
	}
	else{
		printf("%d\n",max);
	}
	return 0;
}
/**************************************************************
	Problem: 1625
	User: xiaojingxuan
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/