#include <iostream>   #include <iomanip>   #include <cstdio>   #include <vector>   #include <algorithm>   #include <cmath>   #include <cstring>   #include <cassert>   #include <string>   #include <set>   #include <map>   #include <random>   #include <bitset>   #include <string>   #include <unordered_set>   #include <unordered_map>   #include <deque>   #include <queue>   #define rep(i, n) for (int i = 0; i < (n); i++)   #define all(x) (x).begin(), (x).end()   #define rall(x) (x).rbegin(), (x).rend()      using namespace std;   using ll = long long;   using ul = unsigned long long;   using ld = long double;      int main() {     ios_base::sync_with_stdio(0); cin.tie(0);     int k;     string s;     cin >> k >> s;     int n = 1 << k, pos = 0;     vector<int> a(n * 2, 1), num(n * 2), rn(n);     for (int i = k - 1; i >= 0; --i)       rep(j, 1 << i) {         num[(1 << i) + j] = pos;         rn[pos] = (1 << i) + j;         ++pos;       }     auto rel = [&](int v, char c) {       if (c ==  0 )         a[v] = a[v * 2];       else if (c ==  1 )         a[v] = a[v * 2 + 1];       else         a[v] = a[v * 2] + a[v * 2 + 1];     };     for (int i = n - 1; i; --i)       rel(i, s[num[i]]);     int q;     cin >> q;     while (q--) {       int v;       char c;       cin >> v >> c;       --v;       s[v] = c;       v = rn[v];       while (v > 0) {         rel(v, s[num[v]]);         v /= 2;       }       cout << a[1] <<   n ;     }   }      