Allen and Bessie are playing a simple number game. They both know a function $f: \{0, 1\}^n \to \mathbb{R}$, i. e. the function takes $n$ binary arguments and returns a real value. At the start of the game, the variables $x_1, x_2, \dots, x_n$ are all set to $-1$. Each round, with equal probability, one of Allen or Bessie gets to make a move. A move consists of picking an $i$ such that $x_i = -1$ and either setting $x_i \to 0$ or $x_i \to 1$.

After $n$ rounds all variables are set, and the game value resolves to $f(x_1, x_2, \dots, x_n)$. Allen wants to maximize the game value, and Bessie wants to minimize it.

Your goal is to help Allen and Bessie find the expected game value! They will play $r+1$ times though, so between each game, exactly one value of $f$ changes. In other words, between rounds $i$ and $i+1$ for $1 \le i \le r$, $f(z_1, \dots, z_n) \to g_i$ for some $(z_1, \dots, z_n) \in \{0, 1\}^n$. You are to find the expected game value in the beginning and after each change.


-----Input-----

The first line contains two integers $n$ and $r$ ($1 \le n \le 18$, $0 \le r \le 2^{18}$).

The next line contains $2^n$ integers $c_0, c_1, \dots, c_{2^n-1}$ ($0 \le c_i \le 10^9$), denoting the initial values of $f$. More specifically, $f(x_0, x_1, \dots, x_{n-1}) = c_x$, if $x = \overline{x_{n-1} \ldots x_0}$ in binary.

Each of the next $r$ lines contains two integers $z$ and $g$ ($0 \le z \le 2^n - 1$, $0 \le g \le 10^9$). If $z = \overline{z_{n-1} \dots z_0}$ in binary, then this means to set $f(z_0, \dots, z_{n-1}) \to g$.


-----Output-----

Print $r+1$ lines, the $i$-th of which denotes the value of the game $f$ during the $i$-th round. Your answer must have absolute or relative error within $10^{-6}$.

Formally, let your answer be $a$, and the jury's answer be $b$. Your answer is considered correct if $\frac{|a - b|}{\max{(1, |b|)}} \le 10^{-6}$.


-----Examples-----
Input
2 2
0 1 2 3
2 5
0 4

Output
1.500000
2.250000
3.250000

Input
1 0
2 3

Output
2.500000

Input
2 0
1 1 1 1

Output
1.000000



-----Note-----

Consider the second test case. If Allen goes first, he will set $x_1 \to 1$, so the final value will be $3$. If Bessie goes first, then she will set $x_1 \to 0$ so the final value will be $2$. Thus the answer is $2.5$.

In the third test case, the game value will always be $1$ regardless of Allen and Bessie's play.

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

ns = {"__name__": "__main__"}
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'import sys\n\nn, r = [int(x) for x in sys.stdin.readline().split()]\na = [int(x) for x in sys.stdin.readline().split()]\ns = sum(a)\nn = 2**n\nsys.stdout.write(str(s / n)+"\\n")\nfor i in range(r):\n\tp, x = [int(x) for x in sys.stdin.readline().split()]\n\ts = s - a[p] + x\n\ta[p] = x\n\tsys.stdout.write(str(s / n)+"\\n")'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

```

Measured memory_bytes: 13555