#include <bits/stdc++.h>
#define MP make_pair
#define PB push_back
#define int long long
#define st first
#define nd second
#define rd third
#define FOR(i, a, b) for(int i =(a); i <=(b); ++i)
#define RE(i, n) FOR(i, 1, n)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REP(i, n) for(int i = 0;i <(n); ++i)
#define VAR(v, i) __typeof(i) v=(i)
#define FORE(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define __builtin_ctz __builtin_ctzll
#define __builtin_clz __builtin_clzll
#define __builtin_popcount __builtin_popcountll
using namespace std;
template<typename TH> void _dbg(const char* sdbg, TH h) { cerr<<sdbg<<"="<<h<<"\n"; }
template<typename TH, typename... TA> void _dbg(const char* sdbg, TH h, TA... t) {
  while(*sdbg != ',') { cerr<<*sdbg++; } cerr<<"="<<h<<","; _dbg(sdbg+1, t...);
}
#ifdef LOCAL
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
#define debugv(x) {{cerr <<#x <<" = "; FORE(itt, (x)) cerr <<*itt <<", "; cerr <<"\n"; }}
#else
#define debug(...) (__VA_ARGS__)
#define debugv(x)
#define cerr if(0)cout
#endif
#define next ____next
#define prev ____prev
#define left ____left
#define hash ____hash
typedef long long ll;
typedef long double LD;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VLL;
typedef vector<pair<int, int> > VPII;
typedef vector<pair<ll, ll> > VPLL;

template<class C> void mini(C&a4, C b4){a4=min(a4, b4); }
template<class C> void maxi(C&a4, C b4){a4=max(a4, b4); }
template<class T1, class T2>
ostream& operator<< (ostream &out, pair<T1, T2> pair) { return out << "(" << pair.first << ", " << pair.second << ")";}
template<class A, class B, class C> struct Triple { A first; B second; C third;
  bool operator<(const Triple& t) const { if (st != t.st) return st < t.st; if (nd != t.nd) return nd < t.nd; return rd < t.rd; } };
template<class T> void ResizeVec(T&, vector<int>) {}
template<class T> void ResizeVec(vector<T>& vec, vector<int> sz) {
  vec.resize(sz[0]); sz.erase(sz.begin()); if (sz.empty()) { return; }
  for (T& v : vec) { ResizeVec(v, sz); }
}
typedef Triple<int, int, int> TIII;
template<class A, class B, class C>
ostream& operator<< (ostream &out, Triple<A, B, C> t) { return out << "(" << t.st << ", " << t.nd << ", " << t.rd << ")"; }
template<class T> ostream& operator<<(ostream& out, vector<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
template<class T> ostream& operator<<(ostream& out, set<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
template<class L, class R> ostream& operator<<(ostream& out, map<L, R> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }


struct Node {
  //int mi, ma;
  int mi, ma;
  int wh_ma;
  //int suf_mi, suf_ma;
  int to_push;
};


const int M = 1 << 20;
Node drz[2 * M + 5];

void Shift(int son, int val) {
  drz[son].mi += val;
  drz[son].ma += val;
  drz[son].to_push += val;
}

void Touch(int v) {
  FOR (son, 2 * v, 2 * v + 1) {
    Shift(son, drz[v].to_push);
  }
  drz[v].to_push = 0;
}
Node Merge(Node L, Node R) {
  Node n;
  n.mi = min(L.mi, R.mi);
  n.ma = max(L.ma, R.ma);
  if (L.ma >= R.ma) {
    n.wh_ma = L.wh_ma;
  } else {
    n.wh_ma = R.wh_ma;
  }
  n.to_push = 0;
  //n.suf_mi
  //n.sum = L.sum + R.sum;
  //   n.mi = min({L.mi, R.mi, n.pref_mi});
  //   n.ma = max(
  return n;
}
void Add(int bl, int br, int l, int r, int v, int val) {
  if (bl > r || br < l) { return; }
  if (l <= bl && br <= r) {
    Shift(v, val);
    return;
  }
  int m = (bl + br) / 2;
  Touch(v);
  Add(bl, m, l, r, 2 * v, val);
  Add(m + 1, br, l, r, 2 * v + 1, val);
  drz[v] = Merge(drz[2 * v], drz[2 * v + 1]);
}



int32_t main() {

  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  cerr << fixed << setprecision(10);
  cin.tie(0);
  //double beg_clock = 1.0 * clock() / CLOCKS_PER_SEC;
  
  string s;
  set<int> or_pos;
  cin>>s;
  int n = SZ(s);
  s = "$" + s;
  VI or_prefs(n + 2);
  RE (i, n) {
    if (s[i] == '?') {
      or_pos.insert(i);
      s[i] = '1';
    }
    if (s[i] == '1') {
      or_prefs[i] = or_prefs[i - 1] + 1;
    } else {
      or_prefs[i] = or_prefs[i - 1] - 1;
    }
  }
  debug(n);
  int res = n;
  REP (tr, 2) {
    set<int> pos = or_pos;
    //VI prefs = or_prefs;
    //vector<Node> drz(2 * M + 5);
    RE (i, n) {
      int add = ((or_prefs[i] % 2) == tr);
      drz[i + M] = {or_prefs[i], or_prefs[i] + add, i, 0};
      if (i == n) {
        debug(or_prefs[i] + add);
      }
    }
    drz[M] = {0, tr == 0, 0, 0};
    FORD (i, M - 1, 0) {
      drz[i] = Merge(drz[2 * i], drz[2 * i + 1]);
//       drz[i].mi = min(drz[2 * i].mi, drz[2 * i + 1].mi);
//       drz[i].ma = max(drz[2 * i].ma, drz[2 * i + 1].ma);
//       if (drz[2 * i].ma >= drz[2 * i + 1].ma) {
//         drz[i].wh_ma = drz[2 * i].wh_ma;
//       } else {
//         drz[i].wh_ma = drz[2 * i + 1].wh_ma;
//       }
//       drz[i].to_push = 0;
    }
    mini(res, drz[1].ma - drz[1].mi);
    debug(drz[1].ma, drz[1].mi);
    while (drz[1].ma >= 2) {
      auto it = pos.upper_bound(drz[1].wh_ma);
      if (it == pos.begin()) { break; }
      it--;
      Add(0, M - 1, *it, n, 1, -2);
      debug(*it, drz[1].ma, drz[1].mi);
      pos.erase(it);
      mini(res, drz[1].ma - drz[1].mi);
    }
  }
  cout<<res<<endl;
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  return 0;
}


Measured memory_bytes: 169788