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:
import sys,os
from io import BytesIO,IOBase
from functools import lru_cache
mod = 10**9+7; Mod = 998244353; INF = float('inf')
# input = lambda: sys.stdin.readline().rstrip("\r\n")
# inp = lambda: list(map(int,sys.stdin.readline().rstrip("\r\n").split()))
#______________________________________________________________________________________________________
# region fastio
# ''' 
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)
# endregion'''
#______________________________________________________________________________________________________
input = lambda: sys.stdin.readline().rstrip("\r\n")
inp = lambda: list(map(int,sys.stdin.readline().rstrip("\r\n").split()))
# ______________________________________________________________________________________________________
# from math import *
# from bisect import *
# from heapq import *
# from collections import defaultdict as dd
# from collections import OrderedDict as odict
# from collections import Counter as cc
# from collections import deque
# from itertools import groupby
# sys.setrecursionlimit(10_100) #this is must for dfs
# ______________________________________________________________________________________________________
# segment tree for range minimum query and update 0 indexing
# init = float('inf')
# st = [init for i in range(4*len(a))]
# def build(a,ind,start,end):
#     if start == end:
#         st[ind] = a[start]
#     else:
#         mid = (start+end)//2
#         build(a,2*ind+1,start,mid)
#         build(a,2*ind+2,mid+1,end)
#         st[ind] = min(st[2*ind+1],st[2*ind+2])
# build(a,0,0,n-1)
# def query(ind,l,r,start,end):
#     if start>r or end<l:
#         return init
#     if l<=start<=end<=r:
#         return st[ind]
#     mid = (start+end)//2
#     return min(query(2*ind+1,l,r,start,mid),query(2*ind+2,l,r,mid+1,end))
# def update(ind,val,stind,start,end):
# 	if start<=ind<=end:
# 		if start==end:
# 			st[stind] = a[start] = val
# 		else:
# 			mid = (start+end)//2
# 			update(ind,val,2*stind+1,start,mid)
# 			update(ind,val,2*stind+2,mid+1,end)
# 			st[stind] = min(st[left],st[right])
# ______________________________________________________________________________________________________
# Checking prime in O(root(N))
# def isprime(n):
#     if (n % 2 == 0 and n > 2) or n == 1: return 0
#     else:
#         s = int(n**(0.5)) + 1
#         for i in range(3, s, 2):
#             if n % i == 0:
#                 return 0
#         return 1
# def lcm(a,b):
#   return (a*b)//gcd(a,b)
# ______________________________________________________________________________________________________
# Merge sort for inversion count
# def mergeSort(left,right,arr,temp):
#     inv_cnt = 0
#     if left<right:
#         mid = (left+right)//2
#         inv1 = mergeSort(left,mid,arr,temp)
#         inv2 = mergeSort(mid+1,right,arr,temp)
#         inv3 = merge(left,right,mid,arr,temp)
#         inv_cnt = inv1+inv3+inv2
#     return inv_cnt
# def merge(left,right,mid,arr,temp):
#     i = left
#     j = mid+1
#     k = left
#     inv = 0
#     while(i<=mid and j<=right):
#         if(arr[i]<=arr[j]):
#             temp[k] = arr[i]
#             i+=1
#         else:
#             temp[k] = arr[j]
#             inv+=(mid+1-i)
#             j+=1
#         k+=1
#     while(i<=mid):
#         temp[k]=arr[i]
#         i+=1
#         k+=1
#     while(j<=right):
#         temp[k]=arr[j]
#         j+=1
#         k+=1
#     for k in range(left,right+1):
#         arr[k] = temp[k]
#     return inv
# ______________________________________________________________________________________________________
# nCr under mod
# def C(n,r,mod = 10**9+7):
#   if r>n: return 0
#   if r>n-r: r = n-r
#   num = den = 1
#   for i in range(r):
#       num = (num*(n-i))%mod
#       den = (den*(i+1))%mod
#   return (num*pow(den,mod-2,mod))%mod
# def C(n,r):
#   if r>n:
#       return 0
#   if r>n-r:
#       r = n-r
#   ans = 1
#   for i in range(r):
#       ans = (ans*(n-i))//(i+1)
#   return ans
# ______________________________________________________________________________________________________
# For smallest prime factor of a number
# M = 10**4+20
# spf = [i for i in range(M)]
# def spfs(M):
#     for i in range(2,M):
#         if spf[i]==i:
#             for j in range(i*i,M,i):
#                 if spf[j]==j:
#                     spf[j] = i

#     return
# spfs(M)
# p = [0]*M
# for i in range(2,M):
#     p[i]+=(p[i-1]+(spf[i]==i))
# ______________________________________________________________________________________________________
# def gtc(p):
#     print('Case #'+str(p)+': ',end='')
# ______________________________________________________________________________________________________
tc = 1
# tc = int(input())
for test in range(1,tc+1):
    n, = inp()
    a = list(input())[::-1]
    n = len(a)
    ans = [0]*(4*n)
    for i in range(n,4*n):
        ans[i] = 1
    for i in range(n-1,-1,-1):
        left = 2*i+1
        right= 2*i+2
        if a[i]=='0':
            ans[i] =ans[right]
        if a[i]=='1':
            ans[i]=ans[left]
        if a[i]=='?':
            ans[i]=ans[left]+ans[right]
    def fill(i,val):
        # a[n-1-i]=val
        a[i] = val
        # print("INTER",end = " ")
        while(True):
            left = 2*i+1
            right= 2*i+2
            if a[i]=='0':
                ans[i] = ans[right]
            if a[i]=='1':
                ans[i] = ans[left]
            if a[i]=='?':
                ans[i]=ans[left]+ans[right]
            if i==0:
                break
            i = (i-1)//2
            # print(i,end = " ")
        # print()
    for q in range(int(input())):
        ind,val = input().split()
        fill(n-int(ind),val)
        # print(a)
        # print(ans[:n+2])
        print(ans[0])