/* Author: Tazim(The_crawler) */
#include<bits/stdc++.h>
#define ll long long int
#define dec greater<int>()
#define lower(s) transform(s.begin(), s.end(), s.begin(), ::tolower);
#define upper(s) transform(s.begin(), s.end(), s.begin(), ::toupper);
#define prow(n) for(auto i:n)cout<<i<<" ";cout<<endl;
#define pcol(n) for(auto i:n)cout<<i<<endl;
#define yes cout<<"YES"<<endl;
#define no cout<<"NO"<<endl;
#define debug(x) cout<<#x<<" = ";_print(x); cout<<endl; /// Debug function
using namespace std; ///****
bool sortbysec(const pair<int, int>& a, const pair<int, int>& b) { return (a.second < b.second); }
template<class T> void _print(T x) { cout << x; }
template<class T> void _print(vector<T>x) { cout << "[ ";for (T i : x)cout << i << " ";cout << "]"; }
template<class T> void _print(set<T>x) { cout << "[ ";for (T i : x)cout << i << " ";cout << "]"; }
template<class T, class V> void _print(pair<T, V>x) { cout << "{" << x.first << "," << x.second << "} "; }
template<class T, class V> void _print(map<T, V>x) { cout << "[ ";for (auto i : x)_print(i);cout << "]"; }
template<class T> void _print(multiset<T>x) { cout << "[ ";for (T i : x)cout << i << " ";cout << "]"; }
/* Hack my code. It's Easy to Read */
 
 
int main() {
   ios_base::sync_with_stdio(false);
   cin.tie(NULL);
   // start
   string s;
   cin >> s;
   int n = s.length();
   map <char, int > mp;
   for (int i = 0; i < n; i++) {
      mp[s[i]]++;
   }
   for (int i = 0; i < s.length(); i++) {
      if (mp[s[i]] - 1 > 0) {
         mp[s[i]]--;
         n--;
      }
      else break;
   }
   for (int i = s.length() - 1; i >= 0; i--) {
      if (mp[s[i]] - 1 > 0) {
         mp[s[i]]--;
         n--;
      }
      else break;
   }
   cout << n << endl;
 
 
 
   return 0;
}