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

long long gcd(long long x, long long y)
{
    if (y == 0)
        return x;
    return gcd(y, x % y);
}

long long lcm(long long x, long long y)
{
    if (x == 0 || y == 0)
        return 0;
    return x / gcd(x, y) * y;
}

int dfs(string s, int l, int r, int cnt)
{
    //cout << s.substr(l, r - l + 1) << endl
    //<< " " << l << " " << r << " " << cnt << endl;

    if (l == r && cnt >= 2)
        return cnt + 1;
    if (r - l < 2)
        return s[r] != s[l] ? cnt : cnt + 2;

    if (cnt > 0 && s[l] != s[r])
        return max(max(dfs(s, l + 1, r, 0), dfs(s, l, r - 1, 0)), dfs(s, l + 1, r - 1, cnt));
    else if (s[l] == s[r])
        return dfs(s, l + 1, r - 1, cnt + 2);
    else
        return max(dfs(s, l + 1, r, 0), dfs(s, l, r - 1, 0));
}

int main()
{
    string S;
    cin >> S;

    int N = S.size();

    cout << dfs(S, 0, N - 1, 0) << endl;
}