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 PYTHON3):

Solution:
#Code by Sounak, IIESTS
#------------------------------warmup----------------------------

import os
import sys
import math
from io import BytesIO, IOBase
import io
from fractions import Fraction
import collections
from itertools import permutations
from collections import defaultdict
from collections import deque
import threading

#sys.setrecursionlimit(300000)
#threading.stack_size(10**8)

BUFSIZE = 8192
 
 
class FastIO(IOBase):
    newlines = 0
    
    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None
     
    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()
 
    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()
 
    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)
 
 
class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")
  
sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")

#-------------------------------------------------------------------------
#mod = 9223372036854775807  
class SegmentTree:
    def __init__(self, data, default=0, func=lambda a, b: a+b):
        """initialize the segment tree with data"""
        self._default = default
        self._func = func
        self._len = len(data)
        self._size = _size = 1 << (self._len - 1).bit_length()
 
        self.data = [default] * (2 * _size)
        self.data[_size:_size + self._len] = data
        for i in reversed(range(_size)):
            self.data[i] = func(self.data[i + i], self.data[i + i + 1])
 
    def __delitem__(self, idx):
        self[idx] = self._default
 
    def __getitem__(self, idx):
        return self.data[idx + self._size]
 
    def __setitem__(self, idx, value):
        idx += self._size
        self.data[idx] = value
        idx >>= 1
        while idx:
            self.data[idx] = self._func(self.data[2 * idx], self.data[2 * idx + 1])
            idx >>= 1
 
    def __len__(self):
        return self._len
 
    def query(self, start, stop):
        if start == stop:
            return self.__getitem__(start)
        stop += 1
        start += self._size
        stop += self._size
 
        res = self._default
        while start < stop:
            if start & 1:
                res = self._func(res, self.data[start])
                start += 1
            if stop & 1:
                stop -= 1
                res = self._func(res, self.data[stop])
            start >>= 1
            stop >>= 1
        return res
 
    def __repr__(self):
        return "SegmentTree({0})".format(self.data)
    
class SegmentTree1:
    def __init__(self, data, default=10**6, func=lambda a, b: min(a,b)):
        """initialize the segment tree with data"""
        self._default = default
        self._func = func
        self._len = len(data)
        self._size = _size = 1 << (self._len - 1).bit_length()
 
        self.data = [default] * (2 * _size)
        self.data[_size:_size + self._len] = data
        for i in reversed(range(_size)):
            self.data[i] = func(self.data[i + i], self.data[i + i + 1])
 
    def __delitem__(self, idx):
        self[idx] = self._default
 
    def __getitem__(self, idx):
        return self.data[idx + self._size]
 
    def __setitem__(self, idx, value):
        idx += self._size
        self.data[idx] = value
        idx >>= 1
        while idx:
            self.data[idx] = self._func(self.data[2 * idx], self.data[2 * idx + 1])
            idx >>= 1
 
    def __len__(self):
        return self._len
 
    def query(self, start, stop):
        if start == stop:
            return self.__getitem__(start)
        stop += 1
        start += self._size
        stop += self._size
 
        res = self._default
        while start < stop:
            if start & 1:
                res = self._func(res, self.data[start])
                start += 1
            if stop & 1:
                stop -= 1
                res = self._func(res, self.data[stop])
            start >>= 1
            stop >>= 1
        return res
 
    def __repr__(self):
        return "SegmentTree({0})".format(self.data)
    
MOD=10**9+7
class Factorial:
    def __init__(self, MOD):
        self.MOD = MOD
        self.factorials = [1, 1]
        self.invModulos = [0, 1]
        self.invFactorial_ = [1, 1]
 
    def calc(self, n):
        if n <= -1:
            print("Invalid argument to calculate n!")
            print("n must be non-negative value. But the argument was " + str(n))
            exit()
        if n < len(self.factorials):
            return self.factorials[n]
        nextArr = [0] * (n + 1 - len(self.factorials))
        initialI = len(self.factorials)
        prev = self.factorials[-1]
        m = self.MOD
        for i in range(initialI, n + 1):
            prev = nextArr[i - initialI] = prev * i % m
        self.factorials += nextArr
        return self.factorials[n]
 
    def inv(self, n):
        if n <= -1:
            print("Invalid argument to calculate n^(-1)")
            print("n must be non-negative value. But the argument was " + str(n))
            exit()
        p = self.MOD
        pi = n % p
        if pi < len(self.invModulos):
            return self.invModulos[pi]
        nextArr = [0] * (n + 1 - len(self.invModulos))
        initialI = len(self.invModulos)
        for i in range(initialI, min(p, n + 1)):
            next = -self.invModulos[p % i] * (p // i) % p
            self.invModulos.append(next)
        return self.invModulos[pi]
 
    def invFactorial(self, n):
        if n <= -1:
            print("Invalid argument to calculate (n^(-1))!")
            print("n must be non-negative value. But the argument was " + str(n))
            exit()
        if n < len(self.invFactorial_):
            return self.invFactorial_[n]
        self.inv(n)  # To make sure already calculated n^-1
        nextArr = [0] * (n + 1 - len(self.invFactorial_))
        initialI = len(self.invFactorial_)
        prev = self.invFactorial_[-1]
        p = self.MOD
        for i in range(initialI, n + 1):
            prev = nextArr[i - initialI] = (prev * self.invModulos[i % p]) % p
        self.invFactorial_ += nextArr
        return self.invFactorial_[n]
 
 
class Combination:
    def __init__(self, MOD):
        self.MOD = MOD
        self.factorial = Factorial(MOD)
 
    def ncr(self, n, k):
        if k < 0 or n < k:
            return 0
        k = min(k, n - k)
        f = self.factorial
        return f.calc(n) * f.invFactorial(max(n - k, k)) * f.invFactorial(min(k, n - k)) % self.MOD
mod=10**9+7
omod=998244353
#---------------------------------Lazy Segment Tree--------------------------------------
# https://github.com/atcoder/ac-library/blob/master/atcoder/lazysegtree.hpp
class LazySegTree:
    def __init__(self, _op, _e, _mapping, _composition, _id, v):
        def set(p, x):
            assert 0 <= p < _n
            p += _size
            for i in range(_log, 0, -1):
                _push(p >> i)
            _d[p] = x
            for i in range(1, _log + 1):
                _update(p >> i)
 
        def get(p):
            assert 0 <= p < _n
            p += _size
            for i in range(_log, 0, -1):
                _push(p >> i)
            return _d[p]
 
        def prod(l, r):
            assert 0 <= l <= r <= _n
 
            if l == r:
                return _e
 
            l += _size
            r += _size
 
            for i in range(_log, 0, -1):
                if ((l >> i) << i) != l:
                    _push(l >> i)
                if ((r >> i) << i) != r:
                    _push(r >> i)
 
            sml = _e
            smr = _e
            while l < r:
                if l & 1:
                    sml = _op(sml, _d[l])
                    l += 1
                if r & 1:
                    r -= 1
                    smr = _op(_d[r], smr)
                l >>= 1
                r >>= 1
 
            return _op(sml, smr)
 
        def apply(l, r, f):
            assert 0 <= l <= r <= _n
            if l == r:
                return
 
            l += _size
            r += _size
 
            for i in range(_log, 0, -1):
                if ((l >> i) << i) != l:
                    _push(l >> i)
                if ((r >> i) << i) != r:
                    _push((r - 1) >> i)
 
            l2 = l
            r2 = r
            while l < r:
                if l & 1:
                    _all_apply(l, f)
                    l += 1
                if r & 1:
                    r -= 1
                    _all_apply(r, f)
                l >>= 1
                r >>= 1
            l = l2
            r = r2
 
            for i in range(1, _log + 1):
                if ((l >> i) << i) != l:
                    _update(l >> i)
                if ((r >> i) << i) != r:
                    _update((r - 1) >> i)
 
        def _update(k):
            _d[k] = _op(_d[2 * k], _d[2 * k + 1])
 
        def _all_apply(k, f):
            _d[k] = _mapping(f, _d[k])
            if k < _size:
                _lz[k] = _composition(f, _lz[k])
 
        def _push(k):
            _all_apply(2 * k, _lz[k])
            _all_apply(2 * k + 1, _lz[k])
            _lz[k] = _id
 
        _n = len(v)
        _log = _n.bit_length()
        _size = 1 << _log
        _d = [_e] * (2 * _size)
        _lz = [_id] * _size
        for i in range(_n):
            _d[_size + i] = v[i]
        for i in range(_size - 1, 0, -1):
            _update(i)
 
        self.set = set
        self.get = get
        self.prod = prod
        self.apply = apply
 
 
MIL = 1 << 20
 
 
def makeNode(total, count):
    # Pack a pair into a float
    return (total * MIL) + count
 
 
def getTotal(node):
    return math.floor(node / MIL)
 
 
def getCount(node):
    return node - getTotal(node) * MIL
 
 
nodeIdentity = makeNode(0.0, 0.0)
 
 
def nodeOp(node1, node2):
    return node1 + node2
    # Equivalent to the following:
    return makeNode(
        getTotal(node1) + getTotal(node2), getCount(node1) + getCount(node2)
    )
 
 
identityMapping = -1
 
 
def mapping(tag, node):
    if tag == identityMapping:
        return node
    # If assigned, new total is the number assigned times count
    count = getCount(node)
    return makeNode(tag * count, count)
 
 
def composition(mapping1, mapping2):
    # If assigned multiple times, take first non-identity assignment
    return mapping1 if mapping1 != identityMapping else mapping2
#-------------------------------------------------------------------------
prime = [True for i in range(10)] 
pp=[0]*10
def SieveOfEratosthenes(n=10):
    p = 2
    c=0
    while (p * p <= n): 
          
        if (prime[p] == True):
            c+=1
            for i in range(p, n+1, p): 
                pp[i]+=1
                prime[i] = False
        p += 1
#---------------------------------Binary Search------------------------------------------
def binarySearch(arr, n, key):
    left = 0
    right = n-1
    mid = 0
    res=arr[n-1]
    while (left <= right):
        mid = (right + left)//2
        if (arr[mid] >= key):
            res=arr[mid]
            right = mid-1
        else:
            left = mid + 1
    return res

def binarySearch1(arr, n, key):
    left = 0
    right = n-1
    mid = 0
    res=arr[0]
    while (left <= right):
        mid = (right + left)//2
        if (arr[mid] > key):
            right = mid-1
        else:
            res=arr[mid]
            left = mid + 1
    return res
#---------------------------------running code------------------------------------------
t=1
#t=int(input())
for _ in range (t):
    k=int(input())
    #a,b,c,d=map(int,input().split())
    #a=list(map(int,input().split()))
    s=input()
    n=2**k-1
    s=list(s)
    s=[0]+s[::-1]
    a=[0]*(2**k)
    #print(s)
    for i in range (2**k-1,0,-1):
        if 2*i <= n:
            if s[i]=='0':
                a[i]=a[2*i+1]
            elif s[i]=='1':
                a[i]=a[2*i]
            else:
                a[i]=a[2*i]+a[2*i+1]
        else:
            if s[i]=='0':
                a[i]=1
            elif s[i]=='1':
                a[i]=1
            else:
                a[i]=2
    #print(a)
    q=int(input())
    for x in range (q):
        p,c=map(str,input().split(' '))
        p=n+1-int(p)
        s[p]=c
        i=p
        while i>=1:
            if 2*i <= n:
                if s[i]=='0':
                    a[i]=a[2*i+1]
                elif s[i]=='1':
                    a[i]=a[2*i]
                else:
                    a[i]=a[2*i]+a[2*i+1]
            else:
                if s[i]=='0':
                    a[i]=1
                elif s[i]=='1':
                    a[i]=1
                else:
                    a[i]=2
            #print(i,a)
            i//=2
        #print(a)
        print(a[1])