#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#define ff first
#define ss second
using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int SZ = 202020;
int n, F[40], dp_a[40][SZ], dp_b[40][SZ];
string T;

int g(int i, int k) {
	assert(k >= 0);
	if (i == n) return 0;
	if (dp_a[k][i] != n) return 1e9;
	if (k < 2) return 1;

	if (dp_a[k - 1][i] == n) {
		return g(i, k - 1);
	}
	else {
		return F[k - 1] + g(dp_a[k - 1][i], k - 2);
	}
}
int h(int i, int k) {
	if (i == 0) return 0;
	if (dp_b[k][i] != 0) return 1e9;
	if (k < 2) return 1;

	if (dp_b[k - 2][i] == 0) {
		return h(i, k - 2);
	}
	else {
		return F[k - 2] + h(dp_b[k - 2][i], k - 1);
	}
}
int f(int k) {
	if (k < 2) {
		return 1e9;
	}
	int ret = f(k - 1);
	for (int i = 1; i < n; i++) {
		ret = min(ret, g(i, k - 2) + h(i, k - 1));
	}
	return ret;
}

int main() {
	cin.tie(0); ios_base::sync_with_stdio(0);
	
	F[0] = 1;
	F[1] = 1;
	for (int i = 2; i <= 30; i++) {
		F[i] = F[i - 1] + F[i - 2];
	} // F[30] = 1346269

	cin >> T;
	n = T.size();

	if (n == 1) {
		return !(cout << 1 << '\n');
	}
	for (int i = 0; i < n; i++) {
		if (T[i] == 'a') {
			dp_a[0][i] = i;
			dp_a[1][i] = i + 1;
		}
		else {
			dp_a[0][i] = i + 1;
			dp_a[1][i] = i;
		}
	}
	for (int i = n; i > 0; i--) {
		if (T[i - 1] == 'a') {
			dp_b[0][i] = i;
			dp_b[1][i] = i - 1;
		}
		else {
			dp_b[0][i] = i - 1;
			dp_b[1][i] = i;
		}
	}

	for (int k = 2; k <= 30; k++) {
		for (int i = 0; i < n; i++) {
			if (dp_a[k - 1][i] == n) dp_a[k][i] = n;
			else dp_a[k][i] = dp_a[k - 2][dp_a[k - 1][i]];
		}
		for (int i = n; i > 0; i--) {
			if (dp_b[k - 2][i] == 0) dp_b[k][i] = 0;
			else dp_b[k][i] = dp_b[k - 1][dp_b[k - 2][i]];
		}
	}
	cout << f(30) << '\n';
}