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

const int N = 150005;
const int C = 32;

int n, ans, len[C], pre[C][N], cntp[C][N], suf[C][N], cnts[C][N];
string s;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	len[0] = len[1] = 1;
	for (int j = 2; j < C; j++) {
		len[j] = len[j - 1] + len[j - 2];
	}
	cin >> s;
	n = s.size();
	for (int i = 0; i < n; i++) {
		pre[0][i] = suf[0][i] = s[i] == 'b';
		cntp[0][i] = cnts[0][i] = 1;
		pre[1][i] = suf[1][i] = s[i] == 'a';
		cntp[1][i] = cnts[1][i] = 1;
	}
	ans = 0x3f3f3f3f;
	for (int j = 2; j < C; j++) {
		for (int i = 0; i < n; i++) {
			if (pre[j - 2][i] == i + 1) {
				pre[j][i] = pre[j - 2][i];
				cntp[j][i] = cntp[j - 2][i];
			} else {
				pre[j][i] = pre[j - 2][i] + pre[j - 1][i - pre[j - 2][i]];
				cntp[j][i] = len[j - 2] + cntp[j - 1][i - pre[j - 2][i]];
			}
			if (suf[j - 1][i] == n - i) {
				suf[j][i] = suf[j - 1][i];
				cnts[j][i] = cnts[j - 1][i];
			} else {
				suf[j][i] = suf[j - 1][i] + suf[j - 2][i + suf[j - 1][i]];
				cnts[j][i] = len[j - 1] + cnts[j - 2][i + suf[j - 1][i]];
			}
		}
		for (int i = 0; i + 1 < n; i++) {
			if (pre[j - 1][i] == i + 1 && suf[j - 2][i + 1] == n - i - 1) {
				ans = min(ans, cntp[j - 1][i] + cnts[j - 2][i + 1]);
			}
		}
	}
	cout << ans << '\n';

	return 0;
}