#include <bits/stdc++.h>
#define mp make_pair
#define fi first
#define se second
#define pb push_back
#define bit(n) (1LL << (n))
#define getbit(x, i) (((x) >> (i)) & 1)
#define pii pair<int, int>
#define ALL(x) (x).begin(), (x).end()
#define sz(x) ((int) (x).size())
using namespace std;
const int M = 5e5 + 5;
const int N = 2e5 + 5;
const int mod = 1e9 + 7;
const int oo = 1e9;
const long long ooo = 1e18;
const double pi = acos(-1);

template<typename T1, typename T2> bool mini(T1 &a, T2 b) {if(a > b) a = b; else return 0; return 1;}
template<typename T1, typename T2> bool maxi(T1 &a, T2 b) {if(a < b) a = b; else return 0; return 1;}

typedef long long ll;

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    #ifdef LOCAL
    freopen("file.inp", "r",stdin);
    #endif
    vector<string> str(60);
    vector<vector<int>> ind(60);
    str[0] = "b";
    str[1] = "a";
    ind[0].resize(1), ind[1] = ind[0];
    ind[0][0] = 0;
    ind[1][0] = 1;

    int k = 29;
    for (int i = 2; i < k; i++) {
        str[i] = str[i - 1] + str[i - 2];
        
        ind[i].resize(sz(str[i]));
        ind[i][0] = i;
        
        for (int j = 1; j < sz(str[i - 1]); j++) {
            ind[i][j] = ind[i - 1][j];
        }

        for (int j = 0; j < sz(str[i - 2]); j++) {
            ind[i][j + sz(str[i - 1])] = ind[i - 2][j];
        }
    }

    string t; cin >> t;

    vector<vector<int>> dp(sz(t) + 1, vector<int>(60, 0));

    for (int i = 0; i < sz(t); i++) {
        dp[i][0] = (t[i] == 'b');
        dp[i][1] = (t[i] == 'a');
    }

    for (int j = 2; j < k; j++) {
        for (int i = 0; i < sz(t); i++) {
            dp[i][j] = dp[i][j - 1] + dp[i + dp[i][j - 1]][j - 2];
        }
    }   

    int ans = oo;

    int n = sz(str[k - 1]), m = sz(t);
    for (int i = 0; i < n; i++) {
        int cur = 0, j = i;
        while (cur < m && j < n) {
            int mx = ind[k - 1][j];
            
            while (mx > 0 && cur + dp[cur][mx - 1] == m) {
                mx--;
            }

            cur += dp[cur][mx];
            // cerr << cur << " " << mx << " " << dp[cur][mx] << "\n";
            j += sz(str[mx]);
        }

        if (cur == m) {
            mini(ans, j - i);
        }
    }

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