#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...) void(0)
#endif

template <class T> std::istream& operator>>(std::istream& is, std::vector<T>& v) {
    for (auto& e : v) {
        is >> e;
    }
    return is;
}

template <class T> std::ostream& operator<<(std::ostream& os, const std::vector<T>& v) {
    for (std::string_view sep = ""; const auto& e : v) {
        os << std::exchange(sep, " ") << e;
    }
    return os;
}

template <class T, class U = T> bool chmin(T& x, U&& y) {
    return y < x and (x = std::forward<U>(y), true);
}

template <class T, class U = T> bool chmax(T& x, U&& y) {
    return x < y and (x = std::forward<U>(y), true);
}

template <class T> void mkuni(std::vector<T>& v) {
    std::ranges::sort(v);
    auto result = std::ranges::unique(v);
    v.erase(result.begin(), result.end());
}

template <class T> int lwb(const std::vector<T>& v, const T& x) {
    return std::distance(v.begin(), std::ranges::lower_bound(v, x));
}

using ll = long long;

using namespace std;

const int MAX = 80;
const ll INF = 1e18;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
    string T;
    cin >> T;

    int n = T.size();
    if (n == 1) {
        cout << 1 << "\n";
        return 0;
    }
    vector<ll> len(MAX);
    len[0] = len[1] = 1;
    for (int i = 2; i < MAX; i++) len[i] = len[i - 1] + len[i - 2];
    vector pre(MAX, vector<pair<int, ll>>(n)), suf(MAX, vector<pair<int, ll>>(n));
    for (int i = 0; i < n; i++) {
        pre[0][i] = (T[i] == 'b' ? make_pair(i - 1, 1) : make_pair(i, 1));
        pre[1][i] = (T[i] == 'a' ? make_pair(i - 1, 1) : make_pair(i, 1));
        suf[0][i] = (T[i] == 'b' ? make_pair(i + 1, 1) : make_pair(i, 1));
        suf[1][i] = (T[i] == 'a' ? make_pair(i + 1, 1) : make_pair(i, 1));
    }
    for (int i = 2; i < MAX; i++) {
        for (int j = 0; j < n; j++) {
            {
                auto [nxt, len] = pre[i - 2][j];
                if (nxt == -1) {
                    pre[i][j] = pre[i - 2][j];
                } else {
                    auto [nnxt, nlen] = pre[i - 1][nxt];
                    pre[i][j] = make_pair(nnxt, len + nlen);
                }
            }
            {
                auto [nxt, len] = suf[i - 1][j];
                if (nxt == n) {
                    suf[i][j] = suf[i - 1][j];
                } else {
                    auto [nnxt, nlen] = suf[i - 2][nxt];
                    suf[i][j] = make_pair(nnxt, len + nlen);
                }
            }
        }
    }

    ll ans = INF;
    for (int i = 1; i < MAX; i++) {
        for (int j = 0; j + 1 < n; j++) {
            auto [l, len1] = pre[i][j];
            auto [r, len2] = suf[i - 1][j + 1];
            if (l == -1 and r == n) chmin(ans, len1 + len2);
        }
    }

    cout << ans << "\n";
    return 0;
}