#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vi vector<ll>
#define pp pair<ll, ll>
#define vvi vector<vi>
#define inf 1000000000
#define rep(i,n) for(int i = 0; i < n; i++)
int pos;
pair<pp, int> createTree(string& s){ //max, min
if(s[pos] == '?'){
pos++;
return {{1, 1}, 1};
}
pair<pp, int> ans;
pair<pp, int> left ,right;
if(s[pos + 1] =='a'){
pos += 4;
left = createTree(s);
pos++;
right = createTree(s);
pos++;
ans.second = left.second + right.second;
ans.first.first = min(left.first.first, right.first.first);
ans.first.second = left.first.second + right.first.second - 1;
}else{
pos += 4;
left = createTree(s);
pos++;
right = createTree(s);
pos++;
ans.second = left.second + right.second;
ans.first.first = left.first.first + right.first.first;
ans.first.second = ans.second - min(left.second - left.first.second, right.second - right.first.second);
}
return ans;
};
int main(){
cin.tie(NULL);
ios_base::sync_with_stdio(false);
string s;
cin >> s;
pos = 0;
pair<pp, int> x = createTree(s);
pp ans = x.first;
cout << ans.second - ans.first + 1 << endl;
}
