#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int mod=1e9+7;
const int N=1000013;
typedef long double ld;
const ld eps=1e-12;
void solve(){
    string s;
    cin>>s;
    ld l=-(sqrtl(5)-1)/2,r=1;
    vector<int>v;
    int cnt=0;
    int ans=0;
    for(auto c:s){
        if(c=='a'){
            if(r<0)l+=1,r+=1,ans++;
            l-=(sqrtl(5)-1)/2,r-=(sqrtl(5)-1)/2;
            r=min(1.0l,r),l=max(-1+eps,l);
        }else{
            if(l>=0)ans++,l-=(sqrtl(5)-1)/2,r-=(sqrtl(5)-1)/2;
            l+=1,r+=1;
            r=min(1.0l,r),l=max(-1+eps,l);
        }
    }
    cout<<ans+s.size()<<'\n';
}


int main(){
    ios::sync_with_stdio(false);
    int T=1;
   // cin>>T;

    while(T--)solve();
}