#include <bits/stdc++.h>

const int MAX_L = 25;

int main() {
    std::string str;

    std::cin >> str;

    int N = str.size();

    str = "#" + str;

    std::vector<std::vector<int>> match(1 + N, std::vector<int>(MAX_L, 0));
    std::vector<std::vector<int>> len(1 + N, std::vector<int>(MAX_L, 0));
    std::vector<int> len_piece(MAX_L, 1);
    for (int i = 2; i < MAX_L; i++)
        len_piece[i] = len_piece[i - 1] + len_piece[i - 2];

    for (int i = 1; i <= N; i++) {
        len[i][0] = len[i][1] = 1;
        if (str[i] == 'b') {
            match[i][0] = i - 1;
            match[i][1] = i;
        } else {
            match[i][0] = i;
            match[i][1] = i - 1;
        }
    }

    for (int l = 2; l < MAX_L; l++) {
        for (int i = 1; i <= N; i++) {
            match[i][l] = match[match[i][l - 2]][l - 1];
            len[i][l] = len[i][l - 2] + len[match[i][l - 2]][l - 1];
        }
    }

    int res = 1 << 30;
    for (int i = 1; i <= len_piece.back(); i++) {
        int node = N, sum_len = 0;
        int pos = i;

        std::vector<int> parts;
        for (int l = MAX_L - 1; l > 0; --l)
            if (len_piece[l - 1] <= pos) {
                parts.push_back(l - 1);
                pos -= len_piece[l - 1];
            }

        for (int p = (int)parts.size() - 1; p >= 0; --p) {
            int l = parts[p];

            sum_len += len[node][l];
            node = match[node][l];
        }

        if (node == 0)
            res = std::min(res, sum_len);
    }

    std::cout << res;

    return 0;
}