#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
#define fix(x) fixed << setprecision(x)
#define asc(x) x, vector<x>, greater<x>
#define rep(i, n) for(ll i = 0; i < n; ++i)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}
constexpr ll INFLL = (1LL << 62), MOD = 998244353;
constexpr int INF = (1 << 30);

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    string s;
    cin >> s;
    int n = s.size(), m = 32;
    vector<vector<int>> v(m,vector<int>(n+1));
    vector<int> c(m,0);
    rep(i,m) v[i][n] = n;
    c[0] = c[1] = 1;
    rep(i,n){
        v[0][i] = i + (s[i]=='b');
        v[1][i] = i + (s[i]=='a');
    }
    for(int i=2;i<m;++i){
        rep(j,n){
            v[i][j] = v[i-2][v[i-1][j]];
        }
        c[i] = c[i-1] + c[i-2];
    }
    int ans = INF;
    vector<vector<int>> memo(m,vector<int>(n+1,-1));
    auto f = [&](auto self, int i, int x) -> int {
        if(memo[x][i]!=-1) return memo[x][i];
        int res = 0;
        if(v[x][i]==n){
            if(x<=1) return memo[x][i] = 1;
            int y = x;
            while(v[x][i]==n){
                if(x==2){
                    res = (v[1][i]!=n) + 1;
                    while(y>x) memo[y--][i] = res;
                    return memo[x][i] = res;
                }
                --x;
            }
            res = c[x] + self(self, v[x][i], x-1);
            while(y>x) memo[y--][i] = res;
            return memo[x][i] = res;
        }
        res = INF;
        for(int y=x+1;y<m;y+=2){
            chmin(res, self(self, v[x][i], y));
        }
        return memo[x][i] = res + c[x];
    };
    rep(i,m) chmin(ans, f(f, 0, i));
    cout << ans << '\n';
    return 0;
}