Problem: 2^k teams participate in a playoff tournament. The tournament consists of 2^k - 1 games. They are held as follows: first of all, the teams are split into pairs: team 1 plays against team 2, team 3 plays against team 4 (exactly in this order), and so on (so, 2^{k-1} games are played in that phase). When a team loses a game, it is eliminated, and each game results in elimination of one team (there are no ties). After that, only 2^{k-1} teams remain. If only one team remains, it is declared the champion; otherwise, 2^{k-2} games are played: in the first one of them, the winner of the game "1 vs 2" plays against the winner of the game "3 vs 4", then the winner of the game "5 vs 6" plays against the winner of the game "7 vs 8", and so on. This process repeats until only one team remains.

For example, this picture describes the chronological order of games with k = 3:

<image>

Let the string s consisting of 2^k - 1 characters describe the results of the games in chronological order as follows:

  * if s_i is 0, then the team with lower index wins the i-th game; 
  * if s_i is 1, then the team with greater index wins the i-th game; 
  * if s_i is ?, then the result of the i-th game is unknown (any team could win this game). 



Let f(s) be the number of possible winners of the tournament described by the string s. A team i is a possible winner of the tournament if it is possible to replace every ? with either 1 or 0 in such a way that team i is the champion.

You are given the initial state of the string s. You have to process q queries of the following form: 

  * p c — replace s_p with character c, and print f(s) as the result of the query. 

Input

The first line contains one integer k (1 ≤ k ≤ 18).

The second line contains a string consisting of 2^k - 1 characters — the initial state of the string s. Each character is either ?, 0, or 1.

The third line contains one integer q (1 ≤ q ≤ 2 ⋅ 10^5) — the number of queries.

Then q lines follow, the i-th line contains an integer p and a character c (1 ≤ p ≤ 2^k - 1; c is either ?, 0, or 1), describing the i-th query.

Output

For each query, print one integer — f(s).

Example

Input


3
0110?11
6
5 1
6 ?
7 ?
1 ?
5 ?
1 1


Output


1
2
3
3
5
4

Solution (in JAVA):

Solution:
import java.util.*;
import java.io.*;

import static java.lang.Math.*;

public class Main
{
    static MyScanner scan;
    static PrintWriter pw;
    static long MOD = 1_000_000_007;
    static long INF = 2_000_000_000_000_000_000L;
    static long inf = 2_000_000_000;
    public static void main(String[] args) {
        new Thread(null, null, "_", 1 << 27) {
            public void run() {
                try {
                    solve();
                } catch (Exception e) {
                    e.printStackTrace();
                    System.exit(1);
                }
            }
        }.start();
    }

    static char s[];
    static int map[], rev_map[], tree[];
    static void solve() throws java.lang.Exception {
        //initIo(true, "");
        initIo(false, "");
        StringBuilder sb = new StringBuilder();

        int k = ni();
        int n = (1<<k);
        // pl("n: "+n);
        map = new int[2*n];
        rev_map = new int[2*n];
        tree = new int[2*n];
        int till = n, idx = 1;
        for(int curr=n/2;curr>=1;curr/=2) {
            for(int i=curr;i<till;i++) {
                map[i] = idx;
                rev_map[idx] = i;
                idx++;
            }
            till = curr;
        }

         // pa("map", map);
        s = ne().toCharArray();
        build(1,0,n-1);
//        for(int i=1;i<n;i++) {
//            p(tree[i]);
//        }
//        pl();
        int q = ni();
        while (q-->0) {
            int where = ni();
            s[where-1] = ne().charAt(0);
            update(rev_map[where]);
//            for(int i=1;i<n;i++) {
//                p(tree[i]);
//            }
//            pl();
//            pl();
            sb.append(tree[1]);
            sb.append("\n");
        }
        psb(sb);

        pw.flush();
        pw.close();
    }

    static void merge(int treein) {
        char c = s[map[treein]-1];
        // pl("treein: "+treein+" rev_map[treein]: "+map[treein]+" c: "+c);
        if(c=='0') {
            tree[treein] = tree[2*treein];
        }
        else if(c=='1') {
            tree[treein] = tree[2*treein+1];
        }
        else {
            tree[treein] = tree[2*treein] + tree[2*treein+1];
        }
    }

    static void build(int treein,int low,int high)
    {
        if(low==high)
            tree[treein] = 1;
        else
        {
            int mid = (low+high)>>1;
            build(2*treein,low,mid);
            build(2*treein+1,mid+1,high);
            merge(treein);
        }
    }

    static void update(int treein) {
        // pl("updating: "+treein);
        while (treein>=1) {
            merge(treein);
            treein/=2;
        }
    }

    static void assert_in_range(String varName, int n, int l, int r) {
        if (n >=l && n<=r) return;
        System.out.println(varName + " is not in range. Actual: "+n+" l : "+l+" r: "+r);
        System.exit(1);
    }
    static void assert_in_range(String varName, long n, long l, long r) {
        if (n>=l && n<=r) return;
        System.out.println(varName + " is not in range. Actual: "+n+" l : "+l+" r: "+r);
        System.exit(1);
    }

    static void initIo(boolean isFileIO, String suffix) throws IOException {
        scan = new MyScanner(isFileIO, suffix);
        if(isFileIO) {
            pw = new PrintWriter("/Users/dsds/Desktop/output"+suffix+".txt");
        }
        else {
            pw = new PrintWriter(System.out, true);
        }
    }
    static int ni() throws IOException
    {
        return scan.nextInt();
    }
    static long nl() throws IOException
    {
        return scan.nextLong();
    }
    static double nd() throws IOException
    {
        return scan.nextDouble();
    }
    static String ne() throws IOException
    {
        return scan.next();
    }
    static String nel() throws IOException
    {
        return scan.nextLine();
    }
    static void pl()
    {
        pw.println();
    }
    static void p(Object o)
    {
        pw.print(o+" ");
    }
    static void pl(Object o)
    {
        pw.println(o);
    }
    static void psb(StringBuilder sb)
    {
        pw.print(sb);
    }
    static void pa(String arrayName, Object arr[])
    {
        pl(arrayName+" : ");
        for(Object o : arr)
            p(o);
        pl();
    }
    static void pa(String arrayName, int arr[])
    {
        pl(arrayName+" : ");
        for(int o : arr)
            p(o);
        pl();
    }
    static void pa(String arrayName, long arr[])
    {
        pl(arrayName+" : ");
        for(long o : arr)
            p(o);
        pl();
    }
    static void pa(String arrayName, double arr[])
    {
        pl(arrayName+" : ");
        for(double o : arr)
            p(o);
        pl();
    }
    static void pa(String arrayName, char arr[])
    {
        pl(arrayName+" : ");
        for(char o : arr)
            p(o);
        pl();
    }

    static void pa(String arrayName, TreeSet<Integer> set)
    {
        pl(arrayName+" : ");
        for(Object o : set)
            p(o);
        pl();
    }

    static void pa(String arrayName, boolean arr[])
    {
        pl(arrayName+" : ");
        for(boolean o : arr)
            p(o);
        pl();
    }
    static void pa(String listName, List list)
    {
        pl(listName+" : ");
        for(Object o : list)
            p(o);
        pl();
    }
    static void pa(String arrayName, Object[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(Object o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, int[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(int o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, long[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(long o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, char[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(char o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, double[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(double o : arr[i])
                p(o);
            pl();
        }
    }
    static void pa(String arrayName, boolean[][] arr) {
        pl(arrayName+" : ");
        for(int i=0;i<arr.length;++i) {
            for(boolean o : arr[i])
                p(o);
            pl();
        }
    }
    static class MyScanner
    {
        BufferedReader br;
        StringTokenizer st;
        MyScanner(boolean readingFromFile, String suffix) throws IOException
        {
            if(readingFromFile) {
                br = new BufferedReader(new FileReader("/Users/ddfds/Desktop/input"+suffix+".txt"));
            }
            else {
                br = new BufferedReader(new InputStreamReader(System.in));
            }
        }
        String nextLine()throws IOException
        {
            return br.readLine();
        }
        String next() throws IOException
        {
            if(st==null || !st.hasMoreTokens())
                st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }
        int nextInt() throws IOException
        {
            return Integer.parseInt(next());
        }
        long nextLong() throws IOException
        {
            return Long.parseLong(next());
        }
        double nextDouble() throws IOException
        {
            return Double.parseDouble(next());
        }
    }
}