Problem: There is a sequence $A = a_0, a_1, ..., a_{n-1}$. You are given the following information and questions.

* relate$(x, y, z)$: $a_y$ is greater than $a_x$ by $z$
* diff$(x, y)$: report the difference between $a_x$ and $a_y$ $(a_y - a_x)$

Constraints

* $2 \leq n \leq 100,000$
* $1 \leq q \leq 200,000$
* $0 \leq x, y < n$
* $x \ne y$
* $0 \leq z \leq 10000$
* There are no inconsistency in the given information

Input


$n \; q$
$query_1$
$query_2$
:
$query_q$


In the first line, $n$ and $q$ are given. Then, $q$ information/questions are given in the following format.


0 $x \; y\; z$


or


1 $x \; y$


where '0' of the first digit denotes the relate information and '1' denotes the diff question.

Output

For each diff question, print the difference between $a_x$ and $a_y$ $(a_y - a_x)$.

Example

Input

5 6
0 0 2 5
0 1 2 3
1 0 1
1 1 3
0 1 4 8
1 0 4


Output

2
?
10

Solution (in PYTHON3):

Solution:
class WUnionFind:
    MAX_N = 0
    PAR  = [] 
    RANK = []
    DIFF_WEIGHT=[]

    def __init__(self,n):
        self.MAX_N = n
        self.PAR = [ i for i in range(n)]
        self.RANK= [ 0 ] * n
        self.DIFF_WEIGHT=[ 0 ] * n

    def root(self,x):
        if self.PAR[x] == x:
            return x
        else:
            r = self.root(self.PAR[x])
            self.DIFF_WEIGHT[x] += self.DIFF_WEIGHT[self.PAR[x]]
            self.PAR[x] = r
            return r
    
    def weight(self,x):
        self.root(x)
        return self.DIFF_WEIGHT[x]

    def issame(self,x,y):
        return self.root(x) == self.root(y)

    def diff(self,x,y):
        return self.weight(y)-self.weight(x)

    def merge(self,x,y,w):
        w += self.weight(x)
        w -= self.weight(y)
        x = self.root(x)
        y = self.root(y)
        if x == y:
            return False
        if self.RANK[x] < self.RANK[y]:
            x,y = y,x
            w = -w
        if self.RANK[x] == self.RANK[y]:
            self.RANK[x] += 1

        self.PAR[y] = x
        self.DIFF_WEIGHT[y] = w
        return True


N,Q  = map(int,input().split())
Ans = []
tree = WUnionFind(N+1)

for _ in range(Q):
    s = list(map(int,input().split()))
    if s[0] == 0:
        x = s[1]
        y = s[2]
        w = s[3]
        tree.merge(x,y,w)
    else:
        x = s[1]
        y = s[2]
        if tree.issame(x,y):
            a = tree.diff(x,y)
        else:
            a = '?'
        Ans.append(a)

for a in Ans:
    print(a)