#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class t, class u>
void chmax(t &a, u b) {
  if (a < b) a = b;
}
template <class t, class u>
void chmin(t &a, u b) {
  if (b < a) a = b;
}
template <class t>
using vc = vector<t>;
template <class t>
using vvc = vector<vector<t>>;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
using vi = vc<int>;
using vl = vc<ll>;
ll readl(void) {
  ll x;
  cin >> x;
  return x;
}
int readi(void) {
  int x;
  cin >> x;
  return x;
}
string readstr() {
  string s;
  cin >> s;
  return s;
}
vi readvi(int n, int off = 0) {
  vi v(n);
  for (int i = 0; i < int(n); i++) v[i] = readi(), v[i] += off;
  return v;
}
vl readvl(int n, int off = 0) {
  vl v(n);
  for (int i = 0; i < int(n); i++) v[i] = readl(), v[i] += off;
  return v;
}
template <class t>
void print(t x, int suc = 1) {
  cout << x;
  if (suc == 1) cout << "\n";
  if (suc == 2) cout << " ";
}
template <class t>
void print(const vc<t> &v, int suc = 1) {
  for (int i = 0; i < int(int(v.size())); i++)
    print(v[i], i == int(int(v.size())) - 1 ? 1 : suc);
}
template <class t>
bool inc(t a, t b, t c) {
  return !(c < b || b < a);
}
template <class t>
void compress(vc<t> &v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
template <class t>
int lwb(const vc<t> &v, const t &a) {
  return lower_bound(v.begin(), v.end(), a) - v.begin();
}
template <class t>
struct Compress {
  vc<t> v;
  Compress() = default;
  Compress(const vc<t> &x) { add(x); }
  Compress(const initializer_list<vc<t>> &x) {
    for (auto &p : x) add(p);
  }
  void add(const t &x) { v.emplace_back(x); }
  void add(const vc<t> &x) { copy(x.begin(), x.end(), back_inserter(v)); }
  void build() { compress(v); }
  int get(const t &x) const { return lwb(v, x); }
  vc<t> get(const vc<t> &x) const {
    vc<t> res(x);
    for (auto &p : res) p = get(p);
    return res;
  }
  const t &operator[](int x) const { return v[x]; }
};
void Yes(bool ex = true) {
  cout << "Yes\n";
  if (ex) exit(0);
}
void YES(bool ex = true) {
  cout << "YES\n";
  if (ex) exit(0);
}
void No(bool ex = true) {
  cout << "No\n";
  if (ex) exit(0);
}
void NO(bool ex = true) {
  cout << "NO\n";
  if (ex) exit(0);
}
void orYes(bool x, bool ex = true) {
  if (x)
    Yes(ex);
  else
    No(ex);
}
void orYES(bool x, bool ex = true) {
  if (x)
    YES(ex);
  else
    NO(ex);
}
void Possible(bool ex = true) {
  cout << "Possible\n";
  if (ex) exit(0);
}
void POSSIBLE(bool ex = true) {
  cout << "POSSIBLE\n";
  if (ex) exit(0);
}
void Impossible(bool ex = true) {
  cout << "Impossible\n";
  if (ex) exit(0);
}
void IMPOSSIBLE(bool ex = true) {
  cout << "IMPOSSIBLE\n";
  if (ex) exit(0);
}
void orPossible(bool x, bool ex = true) {
  if (x)
    Possible(ex);
  else
    Impossible(ex);
}
void orPOSSIBLE(bool x, bool ex = true) {
  if (x)
    POSSIBLE(ex);
  else
    IMPOSSIBLE(ex);
}
int gcd(int x, int y) {
  if (x < y) swap(x, y);
  if (x % y == 0) return y;
  return gcd(y, x % y);
}
using uint = unsigned;
using ull = unsigned long long;
template <uint const &MOD>
struct Modular {
  static constexpr uint const &mod = MOD;
  uint v;
  Modular(long long x = 0) { c(x % mod + mod); }
  Modular &c(uint x) {
    v = x < mod ? x : x - mod;
    return *this;
  }
  Modular pow(int k) const {
    Modular res(1), tmp(v);
    while (k) {
      if (k & 1) res *= tmp;
      tmp *= tmp;
      k >>= 1;
    }
    return res;
  }
  Modular inv() const { return pow(mod - 2); }
  Modular operator-() const { return Modular(mod - v); }
  Modular &operator+=(const Modular &x) { return c(v + x.v); }
  Modular &operator-=(const Modular &x) { return c(v + mod - x.v); }
  Modular &operator*=(const Modular &x) {
    v = ull(v) * x.v % mod;
    return *this;
  }
  Modular &operator/=(const Modular &x) { return *this *= x.inv(); }
  Modular operator+(const Modular &x) const { return Modular(*this) += x; }
  Modular operator-(const Modular &x) const { return Modular(*this) -= x; }
  Modular operator*(const Modular &x) const { return Modular(*this) *= x; }
  Modular operator/(const Modular &x) const { return Modular(*this) /= x; }
  friend Modular operator+(long long x, const Modular &y) {
    return Modular(x) + y;
  }
  friend Modular operator-(long long x, const Modular &y) {
    return Modular(x) - y;
  }
  friend Modular operator*(long long x, const Modular &y) {
    return Modular(x) * y;
  }
  friend Modular operator/(long long x, const Modular &y) {
    return Modular(x) / y;
  }
  friend ostream &operator<<(ostream &os, const Modular &x) {
    return os << x.v;
  }
  friend istream &operator>>(istream &is, Modular &x) {
    long long p;
    is >> p;
    x = Modular(p);
    return is;
  }
  bool operator==(const Modular &x) const { return v == x.v; }
  bool operator!=(const Modular &x) const { return v != x.v; }
  bool operator<(const Modular &x) const { return v < x.v; }
  explicit operator bool() const { return v; }
};
uint MODULAR = 998244353;
using Mint = Modular<MODULAR>;
vector<Mint> fact, finv, invs;
void Initfact(int n = (1 << 21) + 10) {
  fact.resize(n + 1), finv.resize(n + 1), invs.resize(n + 1);
  fact[0] = 1;
  for (int i = 1; i <= n; i++) {
    fact[i] = fact[i - 1] * i;
  }
  finv[n] = fact[n].inv();
  for (int i = n - 1; i >= 0; i--) {
    finv[i] = finv[i + 1] * (i + 1);
  }
  invs[0] = 1;
  for (int i = 0; i <= n; i++) {
    invs[i] = finv[i] * fact[i - 1];
  }
}
Mint comb(int n, int k) { return fact[n] * finv[n - k] * finv[k]; }
int a[1000005], ans = INT_MAX / 2 - 100, n;
string s;
int main(void) {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cin >> s;
  n = int(s.size());
  for (int i = n - 1; i >= 0; i--) {
    if (s[i] == '0') {
      a[i] = a[i + 1] - 1;
    } else {
      a[i] = min(0, a[i + 1] + 1);
    }
  }
  int p = 0, mi = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == '0')
      p--;
    else
      p++;
    chmin(mi, p);
  }
  p = 0;
  int ma = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == '0') {
      p--;
    } else if (s[i] == '1') {
      p++;
    } else {
      if (p + a[i] >= mi + 2) {
        p--;
      } else {
        p++;
      }
    }
    chmax(ma, p);
  }
  chmin(ans, ma - mi);
  p = 0, ma = 0;
  for (int i = 0; i < n; i++) {
    if (s[i] == '0') {
      p--;
    } else if (s[i] == '1') {
      p++;
    } else {
      if (p + a[i] >= mi + 1) {
        p--;
      } else {
        p++;
      }
    }
    chmax(ma, p);
  }
  chmin(ans, ma - mi + 1);
  print(ans);
}
