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

using ll = long long;
using ld = long double;

#define all(a) begin(a), end(a)
#define len(a) int((a).size())

constexpr int INF = 1e9;

struct info {
    int n;
    vector<int> max_pref;
    vector<pair<int, int>> for_suf;
    int ans = INF;

    info() {}

    info(char c, string s) {
        n = 1;
        max_pref.push_back(s[0] == c ? 1 : 0);

        for_suf.resize(len(s));
        for (int i = 0; i < len(s); i++) {
            if (s[i] == c) {
                for_suf[i] = {i + 1, 1};
            } else {
                for_suf[i] = {i, 1};
            }
        }
    }
};

info merge(const info &left, const info &right) {
    info res;
    res.ans = min(left.ans, right.ans);

    int n = len(left.max_pref) + len(right.max_pref);
    int m = len(left.for_suf);

    res.max_pref.resize(n);
    for (int i = len(left.max_pref); i < n; i++) {
        res.max_pref[i] = right.max_pref[i - len(left.max_pref)];
    }

    for (int i = 0; i < len(left.max_pref); i++) {
        int suf = left.max_pref[i];
        if (suf == m) {
            res.max_pref[i] = suf;
        } else {
            auto [nsuf, dlen] = right.for_suf[suf];
            if (nsuf == m) {
                res.ans = min(res.ans, len(left.max_pref) - i + dlen);
            }
            res.max_pref[i] = nsuf;
        }
    }

    res.for_suf.resize(m);
    for (int i = 0; i < m; i++) {
        auto [suf, dlen] = left.for_suf[i];
        if (suf == m) {
            res.for_suf[i] = left.for_suf[i];
        } else {
            auto [nsuf, dlen2] = right.for_suf[suf];
            res.for_suf[i] = {nsuf, dlen + dlen2};
        }
    }
    return res;
}

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

    string s;
    cin >> s;
    if (len(s) == 1) {
        cout << "1\n";
        return 0;
    }

    vector<info> fib;
    fib.push_back(info('b', s));
    fib.push_back(info('a', s));
    for (int i = 2;; i++) {
        fib.push_back(merge(fib.back(), fib[len(fib) - 2]));
        if (i >= 5 && fib[i - 2].ans != INF) {
            cout << fib.back().ans << '\n';
            return 0;
        }
    }
}