#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long inf = mod * mod;
const long long d2 = (mod + 1) / 2;
const double EPS = 1e-11;
const double INF = 1e+10;
const double PI = acos(-1.0);
const int C_SIZE = 3100000;
const int UF_SIZE = 3100000;
namespace {
long long fact[C_SIZE];
long long finv[C_SIZE];
long long inv[C_SIZE];
inline long long Comb(int a, int b) {
  if (a < b || b < 0) return 0;
  return fact[a] * finv[b] % mod * finv[a - b] % mod;
}
void init_C(int n) {
  fact[0] = finv[0] = inv[1] = 1;
  for (int i = 2; i < n; i++) {
    inv[i] = (mod - (mod / i) * inv[mod % i] % mod) % mod;
  }
  for (int i = 1; i < n; i++) {
    fact[i] = fact[i - 1] * i % mod;
    finv[i] = finv[i - 1] * inv[i] % mod;
  }
}
long long pw(long long a, long long b) {
  if (a < 0LL) return 0;
  if (b < 0LL) return 0;
  long long ret = 1;
  while (b) {
    if (b % 2) ret = ret * a % mod;
    a = a * a % mod;
    b /= 2;
  }
  return ret;
}
long long pw_mod(long long a, long long b, long long M) {
  if (a < 0LL) return 0;
  if (b < 0LL) return 0;
  long long ret = 1;
  while (b) {
    if (b % 2) ret = ret * a % M;
    a = a * a % M;
    b /= 2;
  }
  return ret;
}
int pw_mod_int(int a, int b, int M) {
  if (a < 0) return 0;
  if (b < 0) return 0;
  int ret = 1;
  while (b) {
    if (b % 2) ret = (long long)ret * a % M;
    a = (long long)a * a % M;
    b /= 2;
  }
  return ret;
}
int ABS(int a) { return max(a, -a); }
long long ABS(long long a) { return max(a, -a); }
double ABS(double a) { return max(a, -a); }
int sig(double r) { return (r < -EPS) ? -1 : (r > +EPS) ? +1 : 0; }
int UF[UF_SIZE];
void init_UF(int n) {
  for (int i = 0; i < n; i++) UF[i] = -1;
}
int FIND(int a) {
  if (UF[a] < 0) return a;
  return UF[a] = FIND(UF[a]);
}
void UNION(int a, int b) {
  a = FIND(a);
  b = FIND(b);
  if (a == b) return;
  if (UF[a] > UF[b]) swap(a, b);
  UF[a] += UF[b];
  UF[b] = a;
}
}  // namespace
char in[1100000];
pair<int, int> segtree[3][1 << 21];
void add(int a, int b, int c, int d, int e, int f) {
  if (d < a || b < c) return;
  if (c <= a && b <= d) {
    segtree[0][e].first += f;
    segtree[1][e].first += f;
    segtree[2][e].first += f;
    return;
  } else {
    add(a, (a + b) / 2, c, d, e * 2, f);
    add((a + b) / 2 + 1, b, c, d, e * 2 + 1, f);
  }
  pair<int, int> t = min(segtree[0][e * 2], segtree[0][e * 2 + 1]);
  segtree[0][e].second = t.second;
  segtree[0][e].first += t.first;
  segtree[0][e * 2].first -= t.first;
  segtree[0][e * 2 + 1].first -= t.first;
  t = min(segtree[1][e * 2], segtree[1][e * 2 + 1]);
  segtree[1][e].second = t.second;
  segtree[1][e].first += t.first;
  segtree[1][e * 2].first -= t.first;
  segtree[1][e * 2 + 1].first -= t.first;
  t = max(segtree[2][e * 2], segtree[2][e * 2 + 1]);
  segtree[2][e].second = t.second;
  segtree[2][e].first += t.first;
  segtree[2][e * 2].first -= t.first;
  segtree[2][e * 2 + 1].first -= t.first;
}
int p[1100000];
set<int> S0;
set<int> S1;
int SZ = (1 << 20);
int main() {
  scanf("%s", in);
  int n = strlen(in);
  for (int i = 0; i <= n; i++) {
    segtree[0][SZ + i] = make_pair(0, i);
    segtree[1][SZ + i] = make_pair(0, -i);
    segtree[2][SZ + i] = make_pair(0, i);
  }
  for (int i = SZ - 1; i > 0; i--) {
    segtree[0][i] = min(segtree[0][i * 2], segtree[0][i * 2 + 1]);
    segtree[1][i] = min(segtree[1][i * 2], segtree[1][i * 2 + 1]);
    segtree[2][i] = max(segtree[2][i * 2], segtree[2][i * 2 + 1]);
  }
  int tmp = 0;
  for (int i = 0; i < n; i++) {
    if (in[i] == '1') {
      tmp++;
    } else if (in[i] == '?') {
      S0.insert(i);
      tmp--;
    } else
      tmp--;
    add(0, SZ - 1, i + 1, i + 1, 1, tmp);
  }
  int ret = mod;
  int CNT = 0;
  while (1) {
    CNT++;
    pair<int, int> L = segtree[0][1];
    pair<int, int> R = segtree[1][1];
    pair<int, int> H = segtree[2][1];
    ret = min(ret, H.first - L.first);
    int pl = L.second;
    int pr = -R.second;
    set<int>::iterator it = S0.lower_bound(pl);
    if (it == S0.begin()) break;
    it--;
    if (CNT < 300000) pr = pl;
    set<int>::iterator it2 = S1.lower_bound(pr);
    int aL = 1 + (*it);
    int aR = n;
    if (it2 != S1.end()) {
      aR = *it2;
    }
    add(0, SZ - 1, aL, aR, 1, 2);
    int f = *it;
    int g = -1;
    if (it2 != S1.end()) g = *it2;
    S0.erase(f);
    S1.insert(f);
    if (g != -1) {
      S1.erase(g);
      S0.insert(g);
    }
  }
  printf("%d\n", ret);
}
