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

using i64 = long long;

string t;
int n;

struct Info {
    int len;
    vector<int> pref, suf, forward, backward;
    // pref : each prefix match t's suffix
    // suf : each suffix match t's prefix
    // forward : start from each position of t, can match to
    // backward : end at each position of t, can match to
    Info() {}
    Info(char ch) {
        len = 1;
        pref = {n - 1 - (ch == t.back())};
        suf = {ch == t.front()};
        forward = backward = vector<int>(n);
        for (int i = 0; i < n; i++) {
            forward[i] = i + (t[i] == ch);
            backward[i] = i - (t[i] == ch);
        }
    }
    friend Info operator+(Info a, Info b) {
        Info c;
        c.len = a.len + b.len;
        c.pref = c.suf = vector<int>(c.len);
        c.forward = c.backward = vector<int>(n);
        for (int i = 0; i < c.len; i++) {
            if (i < a.len) {
                c.pref[i] = a.pref[i];
            } else {
                if (b.pref[i - a.len] >= 0) {
                    c.pref[i] = a.backward[b.pref[i - a.len]];
                } else {
                    c.pref[i] = -1;
                }
            }
        }
        for (int i = 0; i < c.len; i++) {
            if (i < a.len) {
                if (a.suf[i] < n) {
                    c.suf[i] = b.forward[a.suf[i]];
                } else {
                    c.suf[i] = n;
                }
            } else {
                c.suf[i] = b.suf[i - a.len];
            }
        }
        for (int i = 0; i < n; i++) {
            if (a.forward[i] < n) {
                c.forward[i] = b.forward[a.forward[i]];
            } else {
                c.forward[i] = n;
            }
        }
        for (int i = 0; i < n; i++) {
            if (b.backward[i] >= 0) {
                c.backward[i] = a.backward[b.backward[i]];
            } else {
                c.backward[i] = -1;
            }
        }
        return c;
    }
};

constexpr int inf = 1e9;

int work(const Info &a, const Info &b) {
    int res = inf;
    for (int i = 0, j = 0; i < a.len; i++) {
        while (j < b.len && a.suf[i] <= b.pref[j]) {
            j++;
        }
        if (j != b.len) {
            res = min(res, a.len - i + j + 1);
        }
    }
    return res;
}

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

    auto solve = [&]() {
        cin >> t;
        n = t.size();

        if (n == 1) {
            cout << "1\n";
            return;
        }

        Info s1 = Info('a'), s0 = Info('b');

        constexpr int inf = 1e9;
        int cnt = 0, ans = inf;

        while (work(s1, s0) == inf) {
            s0 = s1 + s0;
            swap(s0, s1);
        }

        ans = min(ans, work(s1, s0));
        ans = min(ans, work(s1, s1));
        ans = min(ans, work(s0, s0));

        s0 = s1 + s0;
        swap(s0, s1);

        ans = min(ans, work(s1, s0));
        ans = min(ans, work(s1, s1));
        ans = min(ans, work(s0, s0));

        cout << ans << '\n';
    };
    
    solve();
    
    return 0;
}