#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>

using namespace std;
using namespace boost::multiprecision;

typedef cpp_int BigInt;
typedef cpp_dec_float_100 PreciseFloat;

#define rep(i, n) for(int (i)=0;(i)<(n);(i)++)
#define rrep(i, n) for(int (i)=((n)-1);(i)>=0;(i)--)
#define itn int
#define miele(v) min_element(v.begin(), v.end())
#define maele(v) max_element(v.begin(), v.end())
#define SUM(v) accumulate(v.begin(), v.end(), 0LL)
#define lb(a, key) lower_bound(a.begin(),a.end(),key)
#define ub(a, key) upper_bound(a.begin(),a.end(),key)
#define COUNT(a, key) count(a.begin(), a.end(), key)
#define BITCOUNT(x) __builtin_popcount(x)
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
using P = pair<int, int>;
using WeightedGraph = vector<vector<P>>;
using UnWeightedGraph = vector<vector<int>>;
using Real = long double;
using Point = complex<Real>; //Point and Vector2d is the same!
// p.real() or real(p) -> x軸, p.imag() or imag(p) -> y軸
using Vector2d = complex<Real>;
const int MOD = 1000000007;
const long long INF = 1LL << 60;
const double EPS = 1e-15;
const double PI = 3.14159265358979323846;

template<typename T>
int getIndexOfLowerBound(vector<T> &v, T x) {
    return lower_bound(v.begin(), v.end(), x) - v.begin();
}

template<typename T>
int getIndexOfUpperBound(vector<T> &v, T x) {
    return upper_bound(v.begin(), v.end(), x) - v.begin();
}

template<class T>
inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template<class T>
inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)

istream &operator>>(istream &is, Point &p) {
    Real a, b;
    is >> a >> b;
    p = Point(a, b);
    return is;
}

template<typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &p_var) {
    is >> p_var.first >> p_var.second;
    return is;
}

template<typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &x : vec) is >> x;
    return is;
}

template<typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
    os << pair_var.first << ' ' << pair_var.second;
    return os;
}

template<typename T>
ostream &operator<<(ostream &os, vector<T> &vec) {
    for (int i = 0; i < vec.size(); i++)
        os << vec[i] << ' ';
    return os;
}

template<typename T, typename U>
ostream &operator<<(ostream &os, vector<pair<T, U>> &vec) {
    for (int i = 0; i < vec.size(); i++)
        os << vec[i] << '\n';
    return os;
}

template<typename T>
ostream &operator<<(ostream &os, vector<vector<T>> &df) {
    for (auto &vec : df) os << vec;
    return os;
}

template<typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
    repi(itr, map_var) {
        os << *itr << ' ';
        itr++;
        itr--;
    }
    return os;
}

template<typename T>
ostream &operator<<(ostream &os, set<T> &set_var) {
    repi(itr, set_var) {
        os << *itr << ' ';
        itr++;
        itr--;
    }
    return os;
}

void print() { cout << endl; }

template<class Head, class... Tail>
void print(Head &&head, Tail &&... tail) {
    cout << head;
    if (sizeof...(tail) != 0) cout << " ";
    print(forward<Tail>(tail)...);
}

int main(void) { cin.tie(0); ios::sync_with_stdio(false);
    string s; cin>>s;
    for (int i = 0; i < s.size() / 2; ++i) { // 最初から回文ではない
        if(s[i] != s[s.size() - 1 - i]) {
            print(s.size());
            return 0;
        }
    }
    if(s.size() % 2 == 0) {
        if(COUNT(s, s[0]) == s.size()) { // 全部同じ
            print(0);
        } else {
            print(s.size()-2);
        }
    } else {
        if(COUNT(s, s[0]) == s.size()) { // 全部同じ
            print(-1);
        } else {
            if(s.size() == 3) {
                print(-1);
            } else print(s.size()-2);
        }
    }
}