#include<bits/stdc++.h>
#define rep(i,s,n) for (int i = (int)(s); i < (int)(n); i++)
#define all(v) begin(v),end(v)
using namespace std;
using ll = long long;
bool chmin(auto &a, auto b){ return a > b ? a = b, 1 : 0; }
bool chmax(auto &a, auto b){ return a < b ? a = b, 1 : 0; }

using pli = pair<ll,int>;
using pii = pair<int,int>;

template<typename T>
ostream &operator<<(ostream &os, const vector<T> &v){
    const char* delim = "";
    for (auto &e : v){
        os << exchange(delim, " ") << e;
    }
    return os;
}

void solve(){
    string s; cin >> s;
    int n = s.size();
    // start (0,n)
    // end (i,i), (i,i+1)
    // state (l, r)
    // left : l, right : n-r
    // if abs(right - left) >= 4 : ans >= 4
    // --> abs(right - left) <= 3 is valid
    // --> abs(n-r - l) <= 3 is valid
    // --> -3 <= n-r-l <= 3
    // --> n-3 <= l+r <= n+3
    // dp[l][i] : r is n-3-l + i
    vector<vector<int>> dp(n,vector<int>(7,5));
    auto dfs = [&](auto sfs, int l, int r) -> int {
        if (r - l <= 1) return 0;
        if (!(n-3 <= l + r && l + r <= n+3)) return 4;
        // r == n-3-l+i
        int i = r - (n-3-l);
        if (dp[l][i] != 5){
            return dp[l][i];
        }
        int ret = 4;
        chmin(ret,sfs(sfs,l+1,r)+1);
        chmin(ret,sfs(sfs,l,r-1)+1);
        if (s[l] == s[r-1]){
            chmin(ret,sfs(sfs,l+1,r-1));
        }
        return dp[l][i] = ret;
    };
    int ans = dfs(dfs,0,n);
    if (ans >= 4) ans = -1;
    cout << ans << '\n';
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    solve();
}