VRC

#include<bits/stdc++.h>
using namespace std;
int main()
{
    string s;
    cin>>s;
    int one=0;
    for(int i=0; i<s.size(); i++)
    {
        if(s[i]=='1')
            one++;
    }
    if(one%2)
        s+='1';
    else
        s+='0';

    cout<<s<<endl;
}