#include<bits/stdc++.h>
using namespace std;
using i64 = long long;
#define int i64
#define vi vector<int>
#define vvi vector<vi>
#define vb vector<bool>
#define pii pair<int, int>
#define fi first
#define se second
#define sz(x) (int)(x).size()
signed main(){
ios_base::sync_with_stdio(false); cin.tie(0);
string s;
cin >> s;
int n = count(s.begin(), s.end(), '?');
auto printp = [&](pii &p) -> void {
cout << p.fi << " " << p.se << "\n";
};
int idx = 0;
function<pii()> calc = [&]() -> pii {
if(s[idx++] == '?') return {1, n};
char c = s[idx];
idx += 3;
pii p1 = calc();
idx++;
pii p2 = calc();
idx++;
if(c == 'a'){
return {p1.fi + p2.fi, max(p1.se, p2.se)};
}
else{
return {min(p1.fi, p2.fi), n - (2 * n - p1.se - p2.se) - 1};
}
};
pii range = calc();
//printp(range);
cout << range.se - range.fi + 1 << "\n";
return 0;
}
