题解

#include<iostream>
#include<algorithm>
using namespace std;

bool ispal(string s){
    string b(s);
    reverse(b.begin(),b.end());
    return s==b;
}
int main(){
    string ring;
    cin>>ring;
    while(ispal(ring)){
        ring=ring.substr(0,ring.size()/2);
    }
    cout<<ring.size();
    return 0;
}