#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
template <class T>
using pq = priority_queue<T>;
template <class T>
using pqg = priority_queue<T, vector<T>, greater<T>>;
int scan() { return getchar(); }
void scan(int& a) { cin >> a; }
void scan(long long& a) { cin >> a; }
void scan(char& a) { cin >> a; }
void scan(double& a) { cin >> a; }
void scan(long double& a) { cin >> a; }
void scan(char a[]) { scanf("%s", a); }
void scan(string& a) { cin >> a; }
template <class T>
void scan(vector<T>&);
template <class T, size_t size>
void scan(array<T, size>&);
template <class T, class L>
void scan(pair<T, L>&);
template <class T, size_t size>
void scan(T (&)[size]);
template <class T>
void scan(vector<T>& a) {
  for (auto& i : a) scan(i);
}
template <class T>
void scan(deque<T>& a) {
  for (auto& i : a) scan(i);
}
template <class T, size_t size>
void scan(array<T, size>& a) {
  for (auto& i : a) scan(i);
}
template <class T, class L>
void scan(pair<T, L>& p) {
  scan(p.first);
  scan(p.second);
}
template <class T, size_t size>
void scan(T (&a)[size]) {
  for (auto& i : a) scan(i);
}
template <class T>
void scan(T& a) {
  cin >> a;
}
void IN() {}
template <class Head, class... Tail>
void IN(Head& head, Tail&... tail) {
  scan(head);
  IN(tail...);
}
string stin() {
  string s;
  cin >> s;
  return s;
}
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
vector<int> iota(int n) {
  vector<int> a(n);
  iota(begin(a), end(a), 0);
  return a;
}
template <class T>
void UNIQUE(vector<T>& x) {
  sort(begin(x), end(x));
  x.erase(unique(begin(x), end(x)), x.end());
}
int in() {
  int x;
  cin >> x;
  return x;
}
long long lin() {
  unsigned long long x;
  cin >> x;
  return x;
}
void print() { putchar(' '); }
void print(bool a) { cout << a; }
void print(int a) { cout << a; }
void print(long long a) { cout << a; }
void print(char a) { cout << a; }
void print(string& a) { cout << a; }
void print(double a) { cout << a; }
template <class T>
void print(const vector<T>&);
template <class T, size_t size>
void print(const array<T, size>&);
template <class T, class L>
void print(const pair<T, L>& p);
template <class T, size_t size>
void print(const T (&)[size]);
template <class T>
void print(const vector<T>& a) {
  if (a.empty()) return;
  print(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    cout << " ";
    print(*i);
  }
  cout << endl;
}
template <class T>
void print(const deque<T>& a) {
  if (a.empty()) return;
  print(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    cout << " ";
    print(*i);
  }
}
template <class T, size_t size>
void print(const array<T, size>& a) {
  print(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    cout << " ";
    print(*i);
  }
}
template <class T, class L>
void print(const pair<T, L>& p) {
  cout << '(';
  print(p.first);
  cout << ",";
  print(p.second);
  cout << ')';
}
template <class T>
void print(set<T>& x) {
  for (auto e : x) print(e), cout << " ";
  cout << endl;
}
template <class T>
void print(multiset<T>& x) {
  for (auto e : x) print(e), cout << " ";
  cout << endl;
}
template <class T, size_t size>
void print(const T (&a)[size]) {
  print(a[0]);
  for (auto i = a; ++i != end(a);) {
    cout << " ";
    print(*i);
  }
}
template <class T>
void print(const T& a) {
  cout << a;
}
int out() {
  putchar('\n');
  return 0;
}
template <class T>
int out(const T& t) {
  print(t);
  putchar('\n');
  return 0;
}
template <class Head, class... Tail>
int out(const Head& head, const Tail&... tail) {
  print(head);
  putchar(' ');
  out(tail...);
  return 0;
}
long long gcd(long long a, long long b) {
  while (b) {
    long long c = b;
    b = a % b;
    a = c;
  }
  return a;
}
long long lcm(long long a, long long b) {
  if (!a || !b) return 0;
  return a * b / gcd(a, b);
}
vector<pair<long long, long long>> factor(long long x) {
  vector<pair<long long, long long>> ans;
  for (long long i = 2; i * i <= x; i++)
    if (x % i == 0) {
      ans.push_back({i, 1});
      while ((x /= i) % i == 0) ans.back().second++;
    }
  if (x != 1) ans.push_back({x, 1});
  return ans;
}
vector<int> divisor(int x) {
  vector<int> ans;
  for (int i = 1; i * i <= x; i++)
    if (x % i == 0) {
      ans.push_back(i);
      if (i * i != x) ans.push_back(x / i);
    }
  return ans;
}
int popcount(long long x) { return __builtin_popcountll(x); }
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int rnd(int n) { return uniform_int_distribution<int>(0, n - 1)(rng); }
template <class... T>
void err(const T&...) {}
struct Setup_io {
  Setup_io() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cout << fixed << setprecision(15);
  }
} setup_io;
const int MAX_ROW = 210;
const int MAX_COL = 210;
struct BitMatrix {
  int H, W;
  bitset<MAX_COL> val[MAX_ROW];
  BitMatrix(int m = 1, int n = 1) : H(m), W(n) {}
  inline bitset<MAX_COL>& operator[](int i) { return val[i]; }
};
int GaussJordan(BitMatrix& A, bool is_extended = false) {
  int rank = 0;
  for (int col = 0; col < A.W; ++col) {
    if (is_extended && col == A.W - 1) break;
    int pivot = -1;
    for (int row = rank; row < A.H; ++row) {
      if (A[row][col]) {
        pivot = row;
        break;
      }
    }
    if (pivot == -1) continue;
    swap(A[pivot], A[rank]);
    for (int row = 0; row < A.H; ++row) {
      if (row != rank && A[row][col]) A[row] ^= A[rank];
    }
    ++rank;
  }
  return rank;
}
int linear_equation(BitMatrix A, vector<int> b, vector<int>& res) {
  int m = A.H, n = A.W;
  BitMatrix M(m, n + 1);
  for (int i = 0; i < m; ++i) {
    for (int j = 0; j < n; ++j) M[i][j] = A[i][j];
    M[i][n] = b[i];
  }
  int rank = GaussJordan(M, true);
  for (int row = rank; row < m; ++row)
    if (M[row][n]) return -1;
  res.assign(n, 0);
  for (int i = 0; i < rank; ++i) res[i] = M[i][n];
  return rank;
}
signed main() {
  string s;
  IN(s);
  int n = s.size();
  int ok = n, ng = 0;
  while (ok - ng > 1) {
    int x = (ok + ng) >> 1;
    bool flag = false;
    bool FLAG = false;
    for (long long i = 0; i < 2; ++i)
      for (long long j = 0; j < 2; ++j) {
        int low = i, high = x - j;
        for (auto e : s) {
          if (e == '?') {
            low--;
            high++;
          }
          if (e == '0') {
            low--;
            high--;
          }
          if (e == '1') {
            low++;
            high++;
          }
          if (low < 0) low += 2;
          if (high > x) high -= 2;
          if (low > high) {
            FLAG = true;
          }
        }
        if (!FLAG) flag = true;
      }
    (flag ? ok : ng) = x;
  }
  cout << ok << '\n';
}
