#include "bits/stdc++.h"
using namespace std;

#define FAST ios_base::sync_with_stdio(false); cin.tie(0);
#define pb push_back
#define eb emplace_back
#define ins insert
#define f first
#define s second
#define cbr cerr<<"hi\n"
#define mmst(x, v) memset((x), v, sizeof ((x)))
#define siz(x) ll(x.size())
#define all(x) (x).begin(), (x).end()
#define lbd(x,y) (lower_bound(all(x),y)-x.begin())
#define ubd(x,y) (upper_bound(all(x),y)-x.begin())
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());    //can be used by calling rng() or shuffle(A, A+n, rng)
inline long long rand(long long x, long long y) { return rng() % (y+1-x) + x; } //inclusivesss
string inline to_string(char c) {string s(1,c);return s;} template<typename T> inline T gcd(T a,T b){ return a==0?llabs(b):gcd(b%a,a); }

using ll=long long; 
using ld=long double;
#define FOR(i,s,e) for(ll i=s;i<=ll(e);++i)
#define DEC(i,s,e) for(ll i=s;i>=ll(e);--i)
using pi=pair<ll,ll>; using spi=pair<ll,pi>; using dpi=pair<pi,pi>; 

#define llinf ((long long)1e18)
#define inf int(1e9+1e6)
#define maxn (1000006)
ll n,psum[maxn];
string A;
int main(){
	FAST
	cin>>A;
	n=A.size();
	A='*'+A;
	FOR(i,1,n){
		psum[i]=psum[i-1]+(A[i] == '1' ? 1 : -1);
	}
	ll Z = *max_element(psum, psum+n+1);
	auto f=[&](ll x){
		mmst(psum,0);
		FOR(i,1,n){
			psum[i]=psum[i-1]+(A[i] == '1' ? 1 : -1);
		}
		vector<ll> suf_max(n+2, -llinf);
		DEC(i,n,1)suf_max[i]=max(suf_max[i+1], psum[i]);
		ll change=0;
		FOR(i,1,n){
			if(A[i] == '?'){
				if(suf_max[i] + 2 * (change+1) <= x) ++ change;
			}
			psum[i] += 2 * change;
		}
		return *min_element(psum, psum+n+1);
	};
	cout<<min(Z - f(Z), Z+1 - f(Z+1))<<'\n';
}
