#include<bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

#define ll long long
#define endl '\n'
#define int ll
using namespace std;
using namespace __gnu_pbds;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int N = 2e5+7, P1 = 31, P2 = 37, mod= 1e9 + 7;

int mul(int a, int b) {
    return (1LL * a * b) % mod;
}

int add(int a, int b) {
    a = (a + mod) % mod;
    b = (b + mod) % mod;
    return (a + b) % mod;
}

int fp(int b, int p) {
    if (b == 1 or p == 0)
        return 1;

    int ret = fp(b, p >> 1);
    ret = mul(ret, ret);

    if (p & 1)
        ret = mul(ret, b);

    return ret;
}

ll modInv(ll n) {
    return fp(n, mod - 2);
}

ll fact[N], inv[N];

void pre() {
    fact[0] = inv[0] = 1;
    for (ll i = 1; i < N; i++)
        fact[i] = (fact[i - 1] * i) % mod, inv[i] = fp(fact[i], mod - 2);
}

ll nCr(ll n, ll r) {
    return ((fact[n] * inv[r]) % mod * inv[n - r]) % mod;
}

ll nPr(ll n, ll r) {
    return ((fact[n] * inv[n - r])) % mod;
}
void doWork() {
    string s;
    cin >> s;
    int n = s.size();
    vector<pair<int,int>> v;
    for (int i = 0; i <  n/2; ++i) {
        if ( s[i] != s[n-1-i])
        {
            pair<int,int> p ={i,i};
            while ((i+1)!= n/2 && (s[i+1] != s[n-1-(i+1)]))
            {
                i++;
            }
            p.second = i;
            //cout << p.first << " " << p.second << endl;
            v.push_back(p);
           // return;
        }
    }
    vector<pair<int,int>> fin;
    for(auto &[i,j] : v)
    {
        if ((fin.size()) && (i == j || (fin.back().first == fin.back().second)))
        {
            // try to merge
            int nw = 0;
            if ( i == j)
            {
                if ( n-1-i -i <= 2)
                    nw = 1;
                else nw = 2;
            }
            else
                 nw = (j-i+2)/2;

            int old = 0;
            if ( fin.back().first == fin.back().second)
            {
                if ( n-1-fin.back().first -fin.back().first <= 2)
                    old = 1;
                else old = 2;
            }
            else
            {
                old =  (fin.back().second-fin.back().first+2) / 2;
            }
            // merge
            int merge =  (j-fin.back().first +2)/2;
            if ( merge < nw+old)
            {
                fin.back().second = j;
            }
        }
        else
        {
            fin.push_back({i,j});
        }
    }
    int ans =0;
    for(auto &[i,j] : fin)
    {
        int nw = 0;
        if ( i == j)
        {
            if ( n-1-i -i <= 2)
                nw = 1;
            else nw = 2;
        }
        else
            nw = (j-i+2)/2;
        ans+=nw;
    }
    cout << ans << endl;
}

signed main() {
    ios::sync_with_stdio(false);
    cout.tie(nullptr);
    cin.tie(nullptr);
//    freopen("bisector.in","r",stdin);
//    freopen("bisector.out","w",stdout);
    int t = 1;
    // cout << primes.size() << endl;
   // cin >> t;
    while (t--) {
        doWork();
    }
    return 0;
}