#include<bits/stdc++.h>
using namespace std;
int main()
{
   int a,num1,num2,temp1,temp2;
   cin>>a;
   if(a>=0)
   {
       cout<<a<<endl;
       exit(0);
   }

   if(a < 0)
   {
       num1 = a;
       num2 = a;
       temp1=num2%10;
       num2=num2/10;
       temp2=num2%10;
       num2=num2-temp2+temp1;
       num1 = num1/10;
   }
   if(num1>num2) cout<<num1<<endl;
   else cout<<num2<<endl;


}