#include <iostream>
using namespace std;
int main()
{
    int b,c,n;
    cin>>n;
    b=n%10;
    c=n/10;
    if(n/10==0) cout<<n;
    if(c==b) cout<<b;
    if((b!=c) && (c!=0)) cout<<0;
    return 0;

}