#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;
using u32 = unsigned;
using u128 = unsigned __int128;

constexpr int K = 40;
constexpr int inf = 1E9;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    std::string t;
    std::cin >> t;
    
    int n = t.size();
    
    std::vector fl(K, std::vector<std::array<int, 2>>(n + 1));
    std::vector fr(K, std::vector<std::array<int, 2>>(n + 1));
    
    for (int k = 0; k < K; k++) {
        fl[k][0] = {0, 0};
        for (int i = 1; i <= n; i++) {
            if (k < 2) {
                if (t[i - 1] == "ba"[k]) {
                    fl[k][i] = {i - 1, 1};
                } else {
                    fl[k][i] = {i, 1};
                }
            } else {
                auto [a, b] = fl[k - 2][i];
                auto [c, d] = fl[k - 1][a];
                fl[k][i] = {c, b + d};
            }
        }
    }
    for (int k = 0; k < K; k++) {
        fr[k][n] = {n, 0};
        for (int i = n - 1; i >= 0; i--) {
            if (k < 2) {
                if (t[i] == "ba"[k]) {
                    fr[k][i] = {i + 1, 1};
                } else {
                    fr[k][i] = {i, 1};
                }
            } else {
                auto [a, b] = fr[k - 1][i];
                auto [c, d] = fr[k - 2][a];
                fr[k][i] = {c, b + d};
            }
        }
    }
    
    int ans = inf;
    if (t.size() == 1) {
        ans = 1;
    }
    for (int k = 2; k < K; k++) {
        for (int i = 0; i <= n; i++) {
            auto [a, b] = fl[k - 1][i];
            auto [c, d] = fr[k - 2][i];
            if (a == 0 && c == n) {
                ans = std::min(ans, b + d);
            }
        }
    }
    
    std::cout << ans << "\n";
    
    return 0;
}