#include //#include //using namespace atcoder; #pragma GCC target ("avx2") #pragma GCC optimization ("O3") #pragma GCC optimization ("unroll-loops") using namespace std; typedef vector VI; typedef vector VVI; typedef vector VS; typedef pair PII; typedef pair pii; typedef pair PLL; typedef pair TIII; typedef long long ll; typedef long double ld; typedef unsigned long long ull; #define FOR(i, s, n) for (int i = s; i < (int)n; ++i) #define REP(i, n) FOR(i, 0, n) #define rep(i, a, b) for (int i = a; i < (b); ++i) #define trav(a, x) for (auto &a : x) #define all(x) x.begin(), x.end() #define MOD 1000000007 template inline bool chmax(T1 &a, T2 b) {if (a < b) {a = b; return true;} return false;} template inline bool chmin(T1 &a, T2 b) {if (a > b) {a = b; return true;} return false;} const double EPS = 1e-8, PI = acos(-1); const double pi = 3.141592653589793238462643383279; //ここから編集 typedef string::const_iterator State; ll GCD(ll a, ll b){ return (b==0)?a:GCD(b, a%b); } ll LCM(ll a, ll b){ return a/GCD(a, b) * b; } template< int mod > struct ModInt { int x; ModInt() : x(0) {} ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {} ModInt &operator+=(const ModInt &p) { if((x += p.x) >= mod) x -= mod; return *this; } ModInt &operator-=(const ModInt &p) { if((x += mod - p.x) >= mod) x -= mod; return *this; } ModInt &operator*=(const ModInt &p) { x = (int) (1LL * x * p.x % mod); return *this; } ModInt &operator/=(const ModInt &p) { *this *= p.inverse(); return *this; } ModInt operator-() const { return ModInt(-x); } ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; } ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; } ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; } ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; } bool operator==(const ModInt &p) const { return x == p.x; } bool operator!=(const ModInt &p) const { return x != p.x; } ModInt inverse() const { int a = x, b = mod, u = 1, v = 0, t; while(b > 0) { t = a / b; swap(a -= t * b, b); swap(u -= t * v, v); } return ModInt(u); } ModInt pow(int64_t n) const { ModInt ret(1), mul(x); while(n > 0) { if(n & 1) ret *= mul; mul *= mul; n >>= 1; } return ret; } friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; } friend istream &operator>>(istream &is, ModInt &a) { int64_t t; is >> t; a = ModInt< mod >(t); return (is); } static int get_mod() { return mod; } }; using modint = ModInt< 998244353 >; template< typename T > struct Combination { vector< T > _fact, _rfact, _inv; Combination(int sz) : _fact(sz + 1), _rfact(sz + 1), _inv(sz + 1) { _fact[0] = _rfact[sz] = _inv[0] = 1; for(int i = 1; i <= sz; i++) _fact[i] = _fact[i - 1] * i; _rfact[sz] /= _fact[sz]; for(int i = sz - 1; i >= 0; i--) _rfact[i] = _rfact[i + 1] * (i + 1); for(int i = 1; i <= sz; i++) _inv[i] = _rfact[i] * _fact[i - 1]; } inline T fact(int k) const { return _fact[k]; } inline T rfact(int k) const { return _rfact[k]; } inline T inv(int k) const { return _inv[k]; } T P(int n, int r) const { if(r < 0 || n < r) return 0; return fact(n) * rfact(n - r); } T C(int p, int q) const { if(q < 0 || p < q) return 0; return fact(p) * rfact(q) * rfact(p - q); } T H(int n, int r) const { if(n < 0 || r < 0) return (0); return r == 0 ? 1 : C(n + r - 1, r); } }; ll modpow(ll x, ll n, ll mod) { ll res = 1; x %= mod; if(x == 0) return 0; while(n) { if(n&1) res = (res * x) % mod; x = (x * x) % mod; n >>= 1; } return res; } inline long long mod(long long a, long long m) { return (a % m + m) % m; } template struct BIT{ int N; std::vector node; BIT(){} BIT(int n){ N = n; node.resize(N+10); } void build(int n) { N = n; node.resize(N+10); } /* a: 1-indexed */ void add(int a, T x){ for(int i=a; i<(int)node.size(); i += i & -i) node[i] += x; } /* [1, a] */ T sum(int a){ T res = 0; for(int x=a; x>0; x -= x & -x) res += node[x]; return res; } /* [l, r] */ T rangesum(int l, int r){ return sum(r) - sum(l-1); } /* a1+a2+...+aw >= valとなるような最小のwを返す @verify https://codeforces.com/contest/992/problem/E */ int lower_bound(T val) { if(val < 0) return 0; int res = 0; int n = 1; while (n < N) n *= 2; T tv=0; for (int k = n; k > 0; k /= 2) { if(res + k < N && node[res + k] < val){ val -= node[res+k]; res += k; } } return res+1; } }; struct UnionFind{ std::vector par; std::vector siz; UnionFind(int sz_): par(sz_), siz(sz_) { for(int i=0; i hash, pow; RollingHash(const string &s) { random_device rnd; mt19937_64 mt(rnd()); base = 1001; n = (int)s.size(); hash.assign(n+1, 0); pow.assign(n+1, 1); for(int i=0; i> 61; ull xd = x & MASK61; ull res = xu + xd; if(res >= mod) res -= mod; return res; } ull mul(ull a, ull b){ ull au = a >> 31; ull ad = a & MASK31; ull bu = b >> 31; ull bd = b & MASK31; ull mid = ad * bu + au * bd; ull midu = mid >> 30; ull midd = mid & MASK30; return calc_mod(au * bu * 2 + midu + (midd << 31) + ad * bd); } //[l,r)のハッシュ値 inline ull get(int l, int r){ ull res = calc_mod(hash[r] + mod*3-mul(hash[l], pow[r-l])); return res; } //string tのハッシュ値 inline ull get(string t){ ull res = 0; for(int i=0; i n) return 0; auto hs = get(t); int res = 0; for(int i=0; i1){ int mid = (lb+ub)/2; if(get(a, a+mid) == get(b, b+mid)) lb = mid; else ub = mid; } return lb; } }; int main() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(12); string s; cin >> s; vector cnt(26); REP(i,s.size()) cnt[s[i]-'a']++; REP(i,26) { if(cnt[i] == s.size()) { if(s.size()%2 == 0) { cout << 0 << endl; }else{ cout << -1 << endl; } return 0; } } int l=0, r=s.size()-1; bool f = true; while(l<=r) { if(s[l] != s[r]) f = false; l++; r--; } if(s.size() == 3) { if(f) cout << -1 << endl; else cout << 3 << endl; }else{ if(f)cout << s.size()-2 << endl; else cout << s.size() << endl; } return 0; }