#include <bits/stdc++.h>
using namespace std;
const int _ = 1.5e5 + 10;
struct node {
	int pos;
	int len;
} f[_][30], g[_][30];
int n, ans = 998244353;
int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	string str;
	cin >> str;
	n = str.length();
	for (int i = 1; i <= n; i++) {
		if (str[i-1] == 'a') {
			f[i][0] = ((node){i + 1, 1});
			g[i][0] = ((node){i - 1, 1});
			f[i][1] = ((node){i, 1});
			g[i][1] = ((node){i, 1});
		} else {
			f[i][0] = ((node){i, 1});
			g[i][0] = ((node){i, 1});
			f[i][1] = ((node){i + 1, 1});
			g[i][1] = ((node){i - 1, 1});
		}
	}
	for (int k = 2; k <= 29; k++) {
		for (int i = 1; i <= n; i++) {
			if (f[i][k-2].pos == 1) {
				f[i][k] = f[i][k-2];
			} else {
				f[i][k] = f[f[i][k-2].pos-1][k-1];
				f[i][k].len += f[i][k-2].len;
			}
			if (g[i][k-1].pos == n) {
				g[i][k] = g[i][k-1];
			} else {
				g[i][k] = g[g[i][k-1].pos+1][k-2];
				g[i][k].len += g[i][k-1].len;
			}
		}
	}
	for (int k = 1; k <= 29; k++) {
		for (int i = 1; i < n; i++) {
			if (f[i][k].pos == 1 && g[i+1][k-1].pos == n) {
				ans = min(ans, f[i][k].len + g[i+1][k-1].len);
			}
		}
	}
	cout << ans << endl;
	return 0;
}