#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

bool check(string s){
	string t(s.rbegin(),s.rend());
	return s==t;
}

int main(){
	
	string s;
	cin>>s;
	
	set<char> S;
	rep(i,s.size())S.insert(s[i]);
	int n = s.size();
	if(!check(s)){
		cout<<n<<endl;
		return 0;
	}
	
	if(n%2==1){
		if(S.size()==1)cout<<-1<<endl;
		else{
			if(n==3){
				cout<<-1<<endl;
			}
			else{
				
			
				cout<<n-2<<endl;
			}
		}
	}
	else{
		if(S.size()==1)cout<<0<<endl;
		else cout<<n-2<<endl;
	}

	return 0;
}