#include<bits/stdc++.h>
using namespace std;

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

string st[40], s;

vector <int> t[4000100];

inline void build(int l, int r, int id) {
	//cout << l << ' ' << r << ' ' << id << endl;
	if (l == r) {
		t[l].push_back(id);
		return;
	}
	int mid = l + st[id - 1].size() - 1;
	build(l, mid, id - 1);
	build(mid + 1, r, id - 2);
	t[l].push_back(id);
}

int f[40][200010];

int main()
{
	st[0] = "b";
	st[1] = "a";
	int cur = 1;
	while (st[cur].size() <= 2000000) {
		++cur;
		st[cur] = st[cur - 1] + st[cur - 2];
	}
	int l = 1, r = st[cur].size();
	build(l, r, cur);
	cin >> s;
	for (int i = 0; i < (int)s.size(); i ++) {
		if (s[i] == 'a') f[1][i] = 1;
		if (s[i] == 'b') f[0][i] = 1;
	}
	for (int i = 2; i <= cur; i ++)
		for (int j = 0; j < (int)s.size(); j ++)
			f[i][j] = f[i - 1][j] + f[i - 2][j + f[i - 1][j]];
	int n = (int)s.size();
	int ans = (int)(st[cur].size());
	//cout << ans << endl;
	for (int j = 1; j <= (int)(st[cur].size()) - (int)(s.size()) - 200000; j ++) {
		int now = j, no = 0;
		//cout << j << ' ' << endl;
		while (now <= (int)(st[cur].size()) && no < n) {
			int L = t[now].size();
			for (int i = L - 1; i >= 0; i --) {
				int cur_id = t[now][i];
				if (no + f[cur_id][no] == n && i != 0) continue;
				now += st[cur_id].size();
				no += f[cur_id][no];
			}
		}
		if (no != n) break;
		ans = min(ans, now - j);
	}
	cout << ans << '\n';
	return 0;
}