#include<iostream>
using namespace std;
string S;
main()
{
	cin>>S;
	bool pari=true;
	for(int i=0;i<S.size();i++)if(S[i]!=S[S.size()-i-1])pari=false;
	if(!pari)
	{
		cout<<S.size()<<endl;
		return 0;
	}
	bool all=true;
	for(int i=0;i<S.size();i++)if(S[i]!=S[0])all=false;
	if(all)
	{
		if(S.size()%2)cout<<-1<<endl;
		else cout<<0<<endl;
		return 0;
	}
	if(S.size()==3)
	{
		cout<<-1<<endl;
		return 0;
	}
	int mid=S.size()/2;
	int alli=-1;
	for(int i=0;i<mid;i++)if(S[i]!=S[0])
	{
		alli=i;
		break;
	}
	cout<<S.size()-2<<endl;
}