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 Node:
    
    def __init__(self, root, length, dist):
        self.root = root
        self.child = None
        self.length = length
        self.dist = dist
        self.tail = root
        
def relate(x, y, z):
    X = A[x].root
    Y = A[y].root
    if A[X].length > A[Y].length:
        x, y, z, X, Y = y, x, -z, Y, X
    T = A[Y].tail
    A[T].child = X
    A[Y].tail = A[X].tail
    A[Y].length += A[X].length
    tmp = X
    xd = A[x].dist
    yd = A[y].dist
    for _ in range(A[X].length):
        A[tmp].root = Y
        A[tmp].dist += yd - z - xd
        tmp = A[tmp].child
    
n,q = [int(i) for i in input().split()]
A = []
for i in range(n):
    A.append(Node(i, 1, 0))
for _ in range(q):
    c = [int(i) for i in input().split()]
    if c[0] == 0 and A[c[1]].root != A[c[2]].root:
        relate(c[1], c[2], c[3])
    elif c[0] == 1:
        if A[c[1]].root == A[c[2]].root:
            print(A[c[2]].dist - A[c[1]].dist)
        else:
            print("?")