#include<bits/stdc++.h>

using namespace std;

typedef long long LL;
vector<LL> decode(string s){
    int n=s.size();
    vector<LL> bits(26,0);
    for(int i=0;i<n;i++){
	bits[s[i]-'A']|=(1ll<<i);
    }
    return bits;
}
int main(){
    string s,t;
    cin>>s;
    t=s;
    reverse(t.begin(),t.end());
    auto S=decode(s);
    auto T=decode(t);
    int res=1,n=s.size();
    for(int i=1,j=n-2;j>0;i++,j--){
	int len=n;
	for(int c=0;c<26;c++){
	    LL diff=(S[c]>>i) xor (T[c]>>j);
	    if(diff==0)continue;
	    len=min(len,__builtin_ctzll(diff)*2-1);
	}
	if(len==n)len=n-2;
	res=max(res,len);
    }
    for(int i=1,j=n-1;i<n;i++,j--){
	int len=n;
	for(int c=0;c<26;c++){
	    LL diff=(S[c]>>i) xor (T[c]>>j);
	    if(diff==0)continue;
	    len=min(len,__builtin_ctzll(diff)*2);
	}
	if(len==n)len=n-2;
	res=max(res,len);
    }
    cout<<res<<endl;
    return 0;
}