#include <bits/stdc++.h>
#define N 5000011
#define link irbvoovr
using namespace std;
char s[N];int n,ch[N*2][2],ed[N*2],link[N*2],len[N*2],siz[N*2],lst,sz;long long ans;
void saminit(){link[0]=-1;len[0]=0;lst=0;}
void append(char s)
{
	int nw=++sz;ed[sz]=1;len[nw]=len[lst]+1;int p=lst;lst=nw;
	while(~p&&!ch[p][s-'a'])ch[p][s-'a']=nw,p=link[p];
	if(!~p){link[nw]=0;return;}
	int q=ch[p][s-'a'];
	if(len[p]+1==len[q])link[lst]=q;
	else
	{
		int cl=++sz;
		link[cl]=link[q];
		for(int i=0;i<2;++i)ch[cl][i]=ch[q][i];
		len[cl]=len[p]+1;
		link[q]=link[nw]=cl;
		while(~p&&ch[p][s-'a']==q)ch[p][s-'a']=cl,p=link[p];
	}
}
char S[N],nS[N];
const int B=5e6;
void dfs(int u,int cur,int len)
{//printf("dfs(%d,%d,%d)\n",u,cur,len);
	if(u==n+1){printf("%d\n",len);exit(0);}
	if(ch[cur][s[u]-'a'])dfs(u+1,ch[cur][s[u]-'a'],len+1);
	if(ch[cur][!(s[u]-'a')])dfs(u,ch[cur][!(s[u]-'a')],len+1);
}
int main()
{
	scanf("%s",s+1);n=strlen(s+1);
	int cnt0=1,cnt1=0;S[1]='a';
	while(cnt0*2+cnt1<=B)
	{
		int nc=0;
		for(int i=1;i<=cnt0+cnt1;++i)
		{
			if(S[i]=='b')nS[++nc]='a';
			else nS[++nc]='a',nS[++nc]='b';
		}
		cnt0=cnt1=0;
		for(int i=1;i<=nc;++i)S[i]=nS[i],cnt0+=S[i]=='a',cnt1+=S[i]=='b';
	}
//	printf("S:%s\n",S+1);
	saminit();
	for(int i=1;i<=cnt0+cnt1;++i)append(S[i]);
	dfs(1,0,0);
}