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:
import sys
from sys import stdin,setrecursionlimit
sys.setrecursionlimit(10**6)
input=stdin.readline
#import pysnooper

class Weighted_Union_find:
    
    def __init__(self,n):
        self.n=n
        self.root=[i for i in range(n+1)]
        self.rank=[0]*(n+1)
        self.weight=[0]*(n+1)

    #@pysnooper.snoop()
    def find_root(self,x):# 頂点xのroot(根)頂点を見つける
        if self.root[x]==x:
            return x
        else:
            y=self.find_root(self.root[x])
            self.weight[x]+=self.weight[self.root[x]]
            self.root[x]=y
            return y
    #@pysnooper.snoop()
    def unite(self,x,y,w):#頂点xと頂点yを繋ぐ辺を追加
        rx=self.find_root(x)
        ry=self.find_root(y)
        if rx==ry:
            return 0
        if self.rank[rx]<self.rank[ry]:
            self.root[rx]=ry
            self.weight[rx]=w-self.weight[x]+self.weight[y]
        else:
            self.root[ry]=rx
            self.weight[ry]=-w-self.weight[y]+self.weight[x]
            if self.rank[rx]==self.rank[ry]:
                self.rank[rx]+=1

    def same(self,x,y):#頂点xと頂点yが連結であるか判定
        return self.find_root(x)==self.find_root(y)

    def count(self,x):#頂点xが属する木のサイズ
        return -self.root[self.find_root(x)]
    
    def diff(self,x,y):#頂点xから頂点yへのコスト
        return self.weight[x]-self.weight[y]

#@pysnooper.snoop()
def main():
    n,q=map(int,input().split())
    gragh=Weighted_Union_find(n+1)
    for _ in range(q):
        query=tuple(map(int,input().split()))
        if not query[0]:
            gragh.unite(query[1],query[2],query[3])
        else:
            if gragh.same(query[1],query[2]):
                print(gragh.diff(query[1],query[2]))
            else:
                print("?")
    #print(1111111111111111)
main()