//DUEL
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define x first
#define y second
#define pii pair<int,int>
#define pb push_back
#define eb emplace_back
#pragma GCC optimize("unroll-loops")
#define shandom_ruffle(a, b) shuffle(a, b, rng)
#define vi vector<int>
#define vl vector<ll>
#define popcnt __builtin_popcount
#define popcntll __builtin_popcountll
#define all(a) begin(a),end(a)

using namespace std;
using namespace __gnu_pbds;

using ll=long long;
using ull=unsigned long long;
using ld=long double;
int MOD=1000000007;
int MOD2=998244353;
vector<int> bases;
const ll LLINF=1ll<<60;
const char en='\n';

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void yes() {cout<<"YES"<<en; exit(0);}
void no() {cout<<"NO"<<en; exit(0);}
inline int rund() {int x576363482791fuweh=rng();return abs(x576363482791fuweh)%RAND_MAX;}
template<class T>
void prVec(vector<T> w,bool fl=false)
{
	cout<<w.size()<<en;
	for (int i=0;i<int(w.size())-1;++i) cout<<w[i]<<' ';
	if (w.size()) cout<<w[w.size()-1]<<en;
	if (fl) cout<<flush;
}

void M998()
{
	swap(MOD,MOD2);
}

ll raand()
{
	ll a=rund();
	a*=RAND_MAX;
	a+=rund();
    return a;
}

#define rand raand

ll raaand()
{
	return raand()*(MOD-7)+raand();
}

void compress(vi&v)
{
	set<int> s;
	for (auto a: v) s.insert(a);
	vi o(all(s));
	for (auto&a: v) a=lower_bound(all(o),a)-o.begin();
}

void compress(vl&v)
{
	set<ll> s;
	for (auto a: v) s.insert(a);
	vl o(all(s));
	for (auto&a: v) a=lower_bound(all(o),a)-o.begin();
}

string to_upper(string a)
{
	for (int i=0;i<(int)a.size();++i) if (a[i]>='a' && a[i]<='z') a[i]-='a'-'A';
	return a;
}

string to_lower(string a)
{
	for (int i=0;i<(int)a.size();++i) if (a[i]>='A' && a[i]<='Z') a[i]+='a'-'A';
	return a;
}

ll sti(string a,int base=10)
{
	ll k=0;
	for (int i=0;i<(int)a.size();++i)
	{
		k*=base;
		k+=a[i]-'0';
	}
	return k;
}

template<class T>
void eras(vector<T>& a,T b)
{
	a.erase(find(a.begin(),a.end(),b));
}

string its(ll k,int base=10)
{
	if (k==0) return "0";
	string a;
	while (k)
	{
		a.push_back((k%base)+'0');
		k/=base;
	}
	reverse(a.begin(),a.end());
	return a;
}

ll min(ll a,int b)
{
	if (a<b) return a;
	return b;
}

ll min(int a,ll b)
{
	if (a<b) return a;
	return b;
}

ll max(ll a,int b)
{
	if (a>b) return a;
	return b;
}

ll max(int a,ll b)
{
	if (a>b) return a;
	return b;
}

ll gcd(ll a,ll b)
{
	if (b==0) return a;
	return gcd(b,a%b);
}

ll lcm(ll a,ll b)
{
	return a/gcd(a,b)*b;
}

template<class T,class K>
pair<T,K> mp(T a,K b)
{
	return make_pair(a,b);
}

inline int mult(ll a,ll b)
{
	return (a*b)%MOD;
}

inline int pot(int n,int k)
{
	if (k==0) return 1;
	ll a=pot(n,k/2);
	a=mult(a,a);
	if (k%2) return mult(a,n);
	else return a;
}

int divide(int a,int b)
{
	return mult(a,pot(b,MOD-2));
}

inline int sub(int a,int b)
{
	if (a-b>=0) return a-b;
	return a-b+MOD;
}

inline int add(int a,int b)
{
	if (a+b>=MOD) return a+b-MOD;
	return a+b;
}

bool prime(ll a)
{
	if (a==1) return 0;
	for (int i=2;i<=round(sqrt(a));++i)
	{
		if (a%i==0) return 0;
	}
	return 1;
}

//const int N=1000010,M=1<<20;
const int N=64,M=64;
int n;
string h;
array<int,7> seg[M*2+10];

array<int,7> mer(array<int,7> a,array<int,7> b)
{
	array<int,7> re;
	re[0]=a[0]+b[0];
	re[1]=max(a[1],a[0]+b[1]);
	re[2]=max(b[2],b[0]+a[2]);
	re[3]=min(a[3],a[0]+b[3]);
	re[4]=min(b[4],b[0]+a[4]);
	re[5]=max(max(a[5],b[5]),a[2]+b[1]);
	re[6]=min(min(a[6],b[6]),a[4]+b[3]);
	/*for (int i=0;i<7;++i) cout<<a[i]<<' ';
	cout<<en;
	for (int i=0;i<7;++i) cout<<b[i]<<' ';
	cout<<en;
	for (int i=0;i<7;++i) cout<<re[i]<<' ';
	cout<<en<<en;*/
	return re;
}

int nev(int x)
{
	int i=1;
	array<int,7> cur={0,0,0,0,0,0,0};
	while (i<M)
	{
		auto c=mer(cur,seg[i*2]);
		if (c[5]<x) cur=c,i=i*2+1;
		else i=i*2;
	}
	return i-M;
}

int nem(int x)
{
	int i=1;
	array<int,7> cur={0,0,0,0,0,0,0};
	while (i<M)
	{
		auto c=mer(cur,seg[i*2]);
		if (c[6]>x) cur=c,i=i*2+1;
		else i=i*2;
	}
	return i-M;
}

void upd(int i,array<int,7> s)
{
	seg[i+=M]=s;
	for (i/=2;i;i/=2) seg[i]=mer(seg[i*2],seg[i*2+1]);
}

array<int,7> jed={1,1,1,0,0,1,0},nul={-1,0,0,-1,-1,0,-1};

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	for (int i=0;i<10;++i) bases.push_back(rand()%(MOD-13893829*2)+13893829);
	cin>>h;
	n=h.size();
	for (int i=0;i<n;++i)
	{
		if (h[i]=='0') seg[i+M]=nul;
		if (h[i]=='1') seg[i+M]=jed;
	}
	for (int i=M-1;i;--i) seg[i]=mer(seg[i*2],seg[i*2+1]);
	int s1=0,s0=0,m1=0,m0=0;
	//cout<<seg[0][5]<<' '<<seg[0][6]<<en;
	for (int i=0;i<n;++i)
	{
		if (h[i]=='?')
		{
			int i1,i2;
			upd(i,jed);
			i1=nev(max(m1,m0)+1);
			upd(i,nul);
			i2=nem(-(max(m1,m0)+1));
			if (i1<i2) h[i]='0';
			else h[i]='1',upd(i,jed);
			//cout<<i<<' '<<i1<<' '<<i2<<en;
		}
		if (h[i]=='0') ++s0,s1=max(0,s1-1);
		else ++s1,s0=max(0,s0-1);
		m1=max(m1,s1);
		m0=max(m0,s0);
	}
	cout<<en<<max(m1,m0)<<en;
}



