#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)), dp(m,vector<int>(n+1,INF));
    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];
    }
    rep(i,m) dp[i][v[i][0]] = c[i];
    int ans = INF;
    rep(i,n){
        rep(j,m){
            rep(k,m){
                if(!(j&1)&&!(k&1)) continue;
                chmin(dp[k][v[k][i]], dp[j][i]+c[k]);
            }
        }
    }
    rep(i,m) chmin(ans, dp[i][n]);
    cout << ans << '\n';
    return 0;
}