#include<bits/stdc++.h>
using namespace std;
int n,ans=1e9;string s;
constexpr int maxn=1.5e5+5;
struct node{
	int val;
	int f1[maxn],f2[maxn],g1[maxn],g2[maxn];
	inline node operator + (const node &o) const{
		node res;
		res.val=val+o.val;
		for(int i=1;i<=n;i++){
			if(f1[i]==n+1) res.f1[i]=f1[i],res.f2[i]=f2[i];
			else res.f1[i]=o.f1[f1[i]],res.f2[i]=val+o.f2[f1[i]];
			if(o.g1[i]==0) res.g1[i]=o.g1[i],res.g2[i]=o.g2[i];
			else res.g1[i]=g1[o.g1[i]],res.g2[i]=o.val+g2[o.g1[i]];
			if(g1[i]==0&&o.f1[i+1]==n+1) ans=min(ans,g2[i]+o.f2[i+1]);
		}
		return res;
	}
}A,B,C;
int main(){
	cin>>s;n=s.length();
	if(n==1) return puts("1"),0;
	A.val=B.val=1;
	for(int i=1;i<=n;i++){
		if(s[i-1]=='a') A.f1[i]=A.g1[i]=i,A.f2[i]=A.g2[i]=0,B.f1[i]=i+1,B.g1[i]=i-1,B.f2[i]=B.g2[i]=1;
		else B.f1[i]=B.g1[i]=i,B.f2[i]=B.g2[i]=0,A.f1[i]=i+1,A.g1[i]=i-1,A.f2[i]=A.g2[i]=1;
	}
	for(int i=1;i<=30;i++) swap(A,B),B=A+B;
	cout<<ans<<'\n';
}