#include <bits/stdc++.h>

using i32 = std::int32_t;
using u32 = std::uint32_t;
using i64 = std::int64_t;
using u64 = std::uint64_t;
using i128 = __int128_t;
using u128 = __uint128_t;
using isize = std::ptrdiff_t;
using usize = std::size_t;

class rep {
    struct Iter {
        usize itr;
        constexpr Iter(const usize pos) noexcept : itr(pos) {}
        constexpr void operator++() noexcept { ++itr; }
        constexpr bool operator!=(const Iter& other) const noexcept { return itr != other.itr; }
        constexpr usize operator*() const noexcept { return itr; }
    };
    const Iter first, last;

  public:
    explicit constexpr rep(const usize first, const usize last) noexcept : first(first), last(std::max(first, last)) {}
    constexpr Iter begin() const noexcept { return first; }
    constexpr Iter end() const noexcept { return last; }
};

template <class T> using Vec = std::vector<T>;

void main_() {
    std::string S;
    std::cin >> S;
    if (S != std::string(S.rbegin(), S.rend())) {
        std::cout << S.size() << '\n';
        return;
    }
    if (std::count(S.begin(), S.end(), S[0]) == (isize)S.size()) {
        std::cout << (S.size() % 2 == 0 ? 0 : -1) << '\n';
        return;
    }
    const auto half = S.size() / 2;
    if (std::count(S.begin(), S.begin() + half, S[0]) == (isize)half) {
        if (S.size() == 3) {
            std::cout << -1 << '\n';
        } else {
            std::cout << S.size() - 2 << '\n';
        }
    } else {
        std::cout << S.size() - 2 << '\n';
    }
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    main_();
    return 0;
}