#include<bits/stdc++.h>

#define ll long long
#define mk make_pair
#define fi first
#define se second

using namespace std;

inline int read(){
	int x=0,f=1;char c=getchar();
	for(;(c<'0'||c>'9');c=getchar()){if(c=='-')f=-1;}
	for(;(c>='0'&&c<='9');c=getchar())x=x*10+(c&15);
	return x*f;
}

const int mod=998244353;
int ksm(int x,ll y,int p=mod){
	int ans=1;y%=(p-1);
	for(int i=y;i;i>>=1,x=1ll*x*x%p)if(i&1)ans=1ll*ans*x%p;
	return ans%p;
}
int inv(int x,int p=mod){return ksm(x,p-2,p)%p;}
mt19937 rnd(time(0));
int randint(int l,int r){return rnd()%(r-l+1)+l;}
void add(int &x,int v){x+=v;if(x>=mod)x-=mod;}
void Mod(int &x){if(x>=mod)x-=mod;}
int cmod(int x){if(x>=mod)x-=mod;return x;}

template<typename T>void cmax(T &x,T v){x=max(x,v);}
template<typename T>void cmin(T &x,T v){x=min(x,v);}

const int N=3e6+5;
const int D=31;

int fib[D],to[D][150005];
string t;

int p=0;
void query(int l,int r,int ql,int qr,int d){
	if(l>r)return ;
	if(l<=ql&&qr<=r)return p=to[d][p],void();
	int mid=ql+fib[d-1]-1;
	if(l<=mid)query(l,r,ql,mid,d-1);
	if(r>mid)query(l,r,mid+1,qr,d-2);
}

int n;
void init(){
	fib[0]=fib[1]=1;n=t.size();
	for(int i=0;i<n;i++){
		to[0][i]=(t[i]=='b'?i+1:i);
		to[1][i]=(t[i]=='a'?i+1:i);
	}
	for(int i=2;i<D;i++){
		fib[i]=fib[i-1]+fib[i-2];
		// cout<<"fib "<<i<<" = "<<fib[i]<<endl;
		for(int j=0;j<n;j++){
			if(to[i-1][j]==n)to[i][j]=n;
			else to[i][j]=to[i-2][to[i-1][j]];
		}
	}
}

void solve(){
	int ans=1e9;
	for(int l=1,r=0;l<=fib[D-1];l++){
		auto chk=[&](){
			p=0;query(l,r,1,fib[D-1],D-1);
			return (p==n);
		};
		while(r<=fib[D-1]&&(chk()==false))r++;
		if(chk())cmin(ans,r-l+1);
	}
	cout<<ans<<endl;
}

signed main(void){

	cin>>t;
	init();
	solve();

	return 0;
}