#include <bits/stdc++.h>
 
using namespace std;

template<ranges::range T, class = enable_if_t<!is_convertible_v<T, string_view>>>
istream& operator>>(istream &s, T &&v) { for (auto &&x : v) s >> x; return s; }
template<ranges::range T, class = enable_if_t<!is_convertible_v<T, string_view>>>
ostream& operator<<(ostream &s, T &&v) { for (auto &&x : v) s << x << ' '; return s; }
 
#ifdef LOCAL
template<class... T> void dbg(T... x) { char e{}; ((cerr << e << x, e = ' '), ...); }
#define debug(x...) dbg(#x, '=', x, '\n')
#else
#define debug(...) ((void)0)
#endif
 
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define ff first
#define ss second
 
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128;
using u128 = unsigned __int128;
using Pt = pair<double, double>;
 
template<class T> inline constexpr T inf = numeric_limits<T>::max() / 2;
constexpr int mod = 1e9 + 7, inv2 = (mod + 1) / 2;
constexpr double eps = 1e-9;
 
template<class T> bool chmin(T &a, T b) { return (b < a and (a = b, true)); }
template<class T> bool chmax(T &a, T b) { return (a < b and (a = b, true)); }

void solve() {
    string S;
    cin >> S;

    string T = string(rall(S));
    int n = S.size();

    vector<int> dp;
    for (int i = 0; i < n; i++)
        for (int j = i + 5; j >= i - 5; j--)
            if (0 <= j and j < n and S[i] == T[j]) {

                int p = j;
                auto it = lower_bound(all(dp), p);
                if (it == dp.end()) {
                    dp.push_back(p);
                } else {
                    chmin(*it, p);
                }
            }

    int x = n - dp.size();
    if (x >= 4) cout << -1 << '\n';
    else cout << x<< '\n';

    
}
 
signed main() {
    cin.tie(0)->sync_with_stdio(false);
    cin.exceptions(cin.failbit);
    int T = 1;
    // cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}