#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using P = pair<ll, ll>;
using Pld = pair<ld, ld>;
using Vec = vector<ll>;
using VecP = vector<P>;
using VecB = vector<bool>;
using VecC = vector<char>;
using VecD = vector<ld>;
using VecS = vector<string>;
using Graph = vector<VecP>;
template <typename T>
using Vec1 = vector<T>;
template <typename T>
using Vec2 = vector<Vec1<T> >;
template <typename T>
bool chmax(T &a, const T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
bool chmin(T &a, const T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
ll pow2(const T n) {
  return (1LL << n);
}
template <typename T>
void cosp(const T n) {
  cout << n << ' ';
}
void co(void) { cout << '\n'; }
template <typename T>
void co(const T n) {
  cout << n << '\n';
}
template <typename T1, typename T2>
void co(pair<T1, T2> p) {
  cout << p.first << ' ' << p.second << '\n';
}
template <typename T>
void co(const Vec1<T> &v) {
  for (T i : v) cosp(i);
  co();
}
template <typename T>
void co(initializer_list<T> v) {
  for (T i : v) cosp(i);
  co();
}
template <typename T>
void ce(const T n) {
  cerr << n << endl;
}
void sonic() {
  ios::sync_with_stdio(false);
  cin.tie(0);
}
void setp(const ll n) { cout << fixed << setprecision(n); }
constexpr int INF = 1e9 + 1;
constexpr ll LINF = 1e18 + 1;
constexpr ll MOD = 1e9 + 7;
constexpr ld EPS = 1e-11;
const ld PI = acos(-1);
int main(void) {
  string s;
  cin >> s;
  while (!s.empty()) {
    if (s.back() == '?')
      s.pop_back();
    else
      break;
  }
  ll n = s.size();
  if (n == 0) {
    co(1);
    return 0;
  }
  ll t = -1;
  ll l = 0, r = n;
  while (r - l > 1) {
    ll m = (l + r) / 2;
    ll mi = 0, ma = m;
    if (ma - mi > 2000) {
      for (ll i = (n)-1; (i) >= (0); --(i)) {
        if (s[i] == '0') {
          ++mi;
          if (ma < m) ++ma;
        } else if (s[i] == '1') {
          --ma;
          if (mi > 0) --mi;
        } else {
          if (mi > 0)
            --mi;
          else if (t > 0)
            ++mi;
          if (ma < m)
            ++ma;
          else if (t > 0)
            --ma;
          if (mi > ma) swap(mi, ma);
        }
        if (mi < 0 || ma > m) {
          mi = LINF;
          break;
        }
        if (mi > ma) break;
      }
      --t;
      if (ma == mi) t = mi + 10000000;
      if (mi <= ma)
        r = m;
      else
        l = m;
    } else {
      bitset<2005> bits(0), range(0);
      for (ll i = (0); (i) < (ma - mi + 1); ++(i)) bits.set(i);
      for (ll i = (0); (i) < (ma - mi + 1); ++(i)) range.set(i);
      for (ll i = (n)-1; (i) >= (0); --(i)) {
        bitset<2005> nxt(0);
        if (s[i] == '0')
          nxt |= bits >> 1;
        else if (s[i] == '1')
          nxt |= bits << 1;
        else {
          nxt |= bits << 1;
          nxt |= bits >> 1;
        }
        nxt &= range;
        swap(nxt, bits);
      }
      if (bits == bitset<2005>(0))
        l = m;
      else
        r = m;
    }
  }
  co(r);
  return 0;
}
