Problem:
Weighted Union Find Trees

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 $a_y$ $(a_y - a_x)$

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 $a_y$ $(a_y - a_x)$.

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

Sample Input

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

Sample Output

2
?
10

Solution in Python3 (judge verdict: Wrong Answer)

MAX = 100000
N, Q =  (int(x) for x in  input().split())
ws = [0 for i in range(MAX)] 
par = [-1 for i in range(MAX)]

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]
    return y


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 False
    ans = ws[x] - ws[y]
    return ans



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)
    else:
        x, y, z = cmd
        unite(x, y, z)