#include<bits/stdc++.h>
using namespace std;
#define rep(i,x,y) for (int i=(x);i<=(y);i++)
#define drep(i,y,x) for (int i=(y);i>=(x);i--)
#define pii pair<int,int>
template<typename T> bool chkmin(T &x, T y){return x>y?x=y,1:0;}
template<typename T> bool chkmax(T &x, T y){return x<y?x=y,1:0;}
void file() {
    #ifdef zqj
    freopen("a.in","r",stdin);
    #endif
}
typedef long long ll;
#define sz 155555

string fib[111]; int m;
int n;
string s;

int dp[sz][111];

void split(int id,int pos,vector<int>&V) {
    if (id<=1) return V.push_back(id),void();
    int tt=fib[id].size()-pos;
    if (tt<=(int)fib[id-2].size()) split(id-2,pos-fib[id-1].size(),V);
    else split(id-1,pos,V),V.push_back(id-2);
}

int main() {
    file();
    ios::sync_with_stdio(false),cin.tie(0);
    fib[0]="b", fib[1]="a";
    for (m=1;fib[m].size()<sz*8;m++) fib[m+1]=fib[m]+fib[m-1];
    cin>>s; n=s.size();
    rep(i,0,n-1) if (s[i]!='a'&&s[i]!='b') s[i]='a';
    rep(j,0,m) dp[n][j]=n;
    drep(i,n-1,0) {
        rep(j,0,1) if (s[i]==fib[j][0]) dp[i][j]=i+1; else dp[i][j]=i;
        rep(j,2,m) dp[i][j]=dp[dp[i][j-1]][j-2];
    }
    cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
    int ans=1e9;
    rep(i,0,(int)fib[m].size()-1-n) {
        vector<int>V;
        split(m,i,V);
        int len=0,t=0,flg=0;
        for (auto x:V) {
            if (dp[t][x]!=n) len+=fib[x].size(),t=dp[t][x];
            else {
                flg=1;
                vector<int>vv({x});
                while (t!=n) {
                    x=vv.back();
                    if (dp[t][x]!=n) len+=fib[x].size(),t=dp[t][x],vv.pop_back();
                    else if (x<=1) ++len,t=n;
                    else vv={x-2,x-1};
                }
            }
        }
        if (flg) chkmin(ans,len);
    }
    cout<<ans<<'\n';
    return 0;
}