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:
# -*- coding: utf-8 -*-

def findSet(x):
  if x == parent[x]:
    return x
  else:
    temp = parent[x]
    parent[x] = findSet(parent[x])
    weight[x] += weight[temp]
    return parent[x]
  
def link(x, y, z):
  a = findSet(x)
  b = findSet(y)
  if a != b:
    parent[b] = a
    weight[b] = weight[x] - weight[y] + z

n, q = list(map(int, input().split()))

data = (i for i in range(n))
parent = [i for i in range(n)]
weight = [0 for i in range(n)]

for i in range(q):
  Ltemp = list(map(int, input().split()))
  if len(Ltemp) == 4:
    x, y, z = Ltemp[1:]
    link(x, y, z)
  else:
    x, y = Ltemp[1:]
    if findSet(x) == findSet(y):
      print(weight[y] - weight[x])
    else:
      print('?')