#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>  
#include <complex>
#include <queue>
#include <set>
#include <unordered_set>
#include <list>
#include <chrono>
#include <random>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <map>
#include <unordered_map>
#include <stack>
#include <iomanip>
#include <fstream>
 
using namespace std;
 
typedef long long ll;
typedef long double ld;
typedef pair<int,int> p32;
typedef pair<ll,ll> p64;
typedef pair<double,double> pdd;
typedef vector<ll> v64;
typedef vector<int> v32;
typedef vector<vector<int> > vv32;
typedef vector<vector<ll> > vv64;
typedef vector<vector<p64> > vvp64;
typedef vector<p64> vp64;
typedef vector<p32> vp32;
ll MOD = 1e9+7;
double eps = 1e-12;
#define forn(i,e) for(ll i = 0; i < e; i++)
#define forsn(i,s,e) for(ll i = s; i < e; i++)
#define rforn(i,s) for(ll i = s; i >= 0; i--)
#define rforsn(i,s,e) for(ll i = s; i >= e; i--)
#define ln "\n"
#define dbg(x) cout<<#x<<" = "<<x<<ln
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define INF 2e18
#define fast_cin() ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())
 
ll mpow(ll a, ll b){
	if(a==0) return 0;
	if(b==0) return 1;
	ll t1 = mpow(a,b/2);
	t1 *= t1;
	t1 %= MOD;
	if(b%2) t1 *= a;
	t1 %= MOD;
	return t1;
}
 
ll mpow(ll a, ll b, ll p){
	if(a==0) return 0;
	if(b==0) return 1;
	ll t1 = mpow(a,b/2,p);
	t1 *= t1;
	t1 %= p;
	if(b%2) t1 *= a;
	t1 %= p;
	return t1;
}
 
ll modinverse(ll a, ll m){
	ll m0 = m; 
    ll y = 0, x = 1; 
    if (m == 1) return 0; 
    while (a > 1){
        ll q = a / m; 
        ll t = m; 
        m = a % m, a = t; 
        t = y; 
        y = x - q * y; 
        x = t; 
    }
    if (x < 0) x += m0; 
    return x; 
}

mt19937_64 mt(chrono::steady_clock::now().time_since_epoch().count());
 
ll range(ll l, ll r){
	return l + mt()%(r-l+1);
}
 
ll rev(ll v){
	return mpow(v,MOD-2);
}

ll n;
v64 a;
string s;

ll check_interval(ll l, ll r){
	// if(l==-1 && r==0) return 0;
	// cout << "check_interval " << l << " " << r << ln;
	ll st = 0, en = 0;
	forn(i,n){
		// cout << i << ln;
		if(s[i]=='?'){
			en+=2;
		}
		ll curl = l+a[i], curr = r+a[i];
		// cout << curl << " " << curr << ln;
		if(curl%2) curl++;
		if(curr%2) curr--;
		// cout << curl << " " << curr << ln;
		// cout << st << " " << en << ln;
		if(en<curl) return -1;
		else if(curr<st) return 1;
		st = max(st,curl);
		en = min(en,curr);
	}
	return 0;
}

bool check(ll len){
	// cout << len << ln;
	ll l = 0,r=len;
	while(l<r){
		ll high = (l+r)/2;
		ll v = check_interval(high-len,high);
		// if(high == 1) cout << v << ln;
		if(v==0) return 1;
		else if(v==-1){
			r = high-1;
		}
		else{
			l = high+1; 
		}
	}
	ll v = check_interval(l-len,l);
	// if(len==0) cout <<  v << ln;
	if(v==0) return 1;
	return 0;
}

void solve(){
	cin >> s;
	n = sz(s);
	ll v[n],sum[n];
	forn(i,n){
		if(s[i]=='1') {
			v[i]=(i ? v[i-1] : 0) + 1;
			sum[i] = (i ? sum[i-1] : 0);
		}
		else if(s[i]=='0') {
			v[i]=(i ? v[i-1] : 0) - 1;
			sum[i] = (i ? sum[i-1] : 0);
		}
		else {
			v[i]=(i ? v[i-1] : 0);
			sum[i] = (i ? sum[i-1] : 0) + 1;
		}
	}
	a.resize(n);
	forn(i,n) a[i] = sum[i]-v[i];
	ll l = 1,r=n;
	while(l!=r){
		ll len = (l+r)/2;
		bool bo = check(len);
		// cout << len << " " << bo << ln;
		if(bo) r = len;
		else l = len+1;
	}
	cout << l << ln;
}
 
int main()
{
	fast_cin();
    ll t=1;
    // cin >> t;
    forn(i,t) {
    	// cout << "Case #" << i+1 << ": ";
    	solve();
    }
    return 0;
}

Measured memory_bytes: 27816