#include <bits/stdc++.h>
using namespace std;
#define int              long long int
#define double           long double
#define print(a)         for(auto x : a) cout << x << " "; cout << endl


const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;

inline int power(int a, int b, int mod=M) {
    int x = 1;
    a %= mod;
    while (b) {
        if (b & 1) x = (x * a) % mod; 
        a = (a * a) % mod;
        b >>= 1;
    }
    return x;
}


//_ ***************************** START Below *******************************




string a;

int consistency(int n){

	vector<int> dpA1(n+1, 0);
	vector<int> dpA2(n+1, 0);
	vector<int> dpB1(n+1, 0);
	vector<int> dpB2(n+1, 0);
	
	dpA1[0] = dpA2[0] = dpB1[0] = dpB2[0] = 0;
	
	if(a[0] == 'a') dpA1[1] = 1;
	else dpB1[1] = 1;
	
	for(int i=2; i<=n; i++){
		
		if(a[i-1] == 'a'){
			dpA1[i] = max(dpB1[i-1] , dpB2[i-1]) + 1;
		}
		if(a[i-1] == 'a' && a[i-2] == 'a'){
			dpA2[i] = max( dpB1[i-2] , dpB2[i-2] ) + 2;
		}
		
		if(a[i-1] == 'b'){
			dpB1[i] = max(dpA1[i-1] , dpA2[i-1] ) + 1;
		}
		if(a[i-1] == 'b' && a[i-2] == 'b'){
			dpB2[i] = max( dpA1[i-2] , dpA2[i-2] ) + 2;
		}
		
	}
	

	int ans = 0;
	for(int i=0; i<=n; i++){
		ans = max({ans, dpA1[i], dpA2[i] , dpB1[i] , dpB2[i] });
	}
	
	return ans;
}















int practice(int n){


    return 0;
}





void solve() {
    
    int n;
    
    cin >> a;
    n = a.size();
    
    cout << consistency(n) << endl;


}





int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}