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:
MAX = 100005
ws = [0 for i in range(MAX)] 
par = [-1 for i in range(MAX*2)]


def weight(x):
    root(x)
    return ws[x]

def root(x):
    if par[x] < 0: return x
    p = root(par[x])
    ws[x] = ws[x] + ws[par[x]]
    par[x] = p
    return par[x]


def unite(y, x, z):
    z = z + weight(x)
    z = z - weight(y)
    x = root(x)
    y = root(y)
    if x == y: return 0
    if par[y] < par[x]:
        tmp = x
        x = y 
        y = tmp 
        z = -z
     
    par[x] = par[x] + par[y]
    par[y] = x
    ws[y] = z
    return 1 

def diff(x,y):
    if root(x) != root(y) :return 0
    ans = ws[x] - ws[y]
    return 1 ,ans


if __name__=='__main__':
   global ans
   N, Q =  (int(x) for x in  input().split())
   for q in range(Q):
        t, *cmd =  (int(x) for x in  input().split())
        if t:
            x, y = cmd
            z = diff(x, y)
            if z==False :print("?")
            else :print(z[1])
        else:
            x, y, z = cmd
            unite(x, y, z)