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:
#!python3

import sys
sys.setrecursionlimit(1000000000)
iim = lambda: map(int, input().rstrip().split())

def resolve():
    N, Q = iim()
    S = [i for i in range(N)]
    W = [0] * N
    R = [0] * N

    def find(x):
        if S[x] == x:
            return x

        i = find(S[x])
        W[x] += W[S[x]]
        S[x] = i
        return i

    def relate(x, y, w):
        i = find(x)
        j = find(y)

        if R[i] < R[j]:
            S[i] = j
            W[i] = w - W[x] + W[y]
        else:
            S[j] = i
            W[j] = -w - W[y] + W[x]
            if R[i] == R[j]:
                R[i] += 1

    def diff(x, y):
        i = find(x)
        j = find(y)

        if i != j: return "?"

        return W[x] - W[y]

    ans = []
    for com, *xyz in (map(int, s.split()) for s in sys.stdin):
        if com == 0:
            relate(*xyz)
        else:
            ans.append(diff(*xyz))
    print(*ans, sep="\n")

if __name__ == "__main__":
    resolve()