#include <bits/stdc++.h>
#define pb push_back
#define ll long long
#define ff first
#define ss second
using namespace std;
string s;
int n;
int cur = 0;
vector<int>test;
struct node{
	node *L, *R;
	int idx;
	bool isMax;
	bool isHoja;
	int xDown;
	int myL, myR;
	node (int l, int &r){
		if(s[l] == '?'){
			//cout << "hoja " << endl;
			idx = cur ++ ;
			isHoja = true;
			xDown = 1;
		}else{
			isHoja = false;
			int cuenta = 0;
			int l2 = 0;
			isMax = s[l+1] == 'a';
			//cout<< "ismax: " << isMax << endl;
			l += 4;
			r += 4;
			//cout << "left " << "\n";
			L = new node(l, r);
			r += 2 ;
			//cout << "right r = " << r  << endl;
			R = new node(r, r);
			r += 1;
			//cout << "ending r = " << r << endl;
			
			
			xDown = L->xDown + R->xDown;
		}
	}

	void prop(){
		if(isHoja){
			myL = 0;
			myR = 0;
		}else{
			L->prop();
			R->prop();
			if(isMax){
				myL = L->myL + R->myL + 1;
				myR = max(L->myR + R->xDown, R->myR + L->xDown);
			}else{
				myL = min(L->myL, R->myL);
				myR = L->myR + R->myR;
			}
		}
		
	}
	
	
};

node *root;
int main(){
	ios::sync_with_stdio(NULL);
	cin.tie(0);
	cout.tie(0);
	#ifdef LOCAL
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
	#endif
	cin >> s;
	n = s.size();
	int r = 0;
	root = new node(0, r);
	
	root->prop();
	//cout << root->myR << " " << root ->myL << endl;
	cout << root->myR-root->myL+1 << "\n";
	return 0;
}