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 CPP):

Solution:
#include<iostream>
#include<cstdio>
#include<vector>
#include<algorithm>
#include<cstring>
#include<stdio.h>
#include<fstream>
#include<stdlib.h>
#include<math.h> 
#include<queue>
#include<string.h>
#include<stack>


using namespace std;

#define INF 1000000000
#define BL 1
#define WH 0
#define GL 2

int par[100001];
int r[100001];
int weight[100001];

void init(int n){
	for(int i=0;i<n;i++){
		par[i]=i;
		weight[i]=0;
		r[i]=0;
	}
}


int root(int x){
	if(par[x]==x){
		return x;
	}
	else {
		int temp=root(par[x]);
		weight[x]+=weight[par[x]];
		return par[x]=temp;
	}
}

bool same(int x,int y){
	return root(x)==root(y);
}


void unite(int x,int y,int w){
	par[x]=root(x);
	par[y]=root(y);
	int a=w-(weight[y]-weight[x]);

	//if(x==y)return;

	if(r[par[x]]>r[par[y]]){
		weight[par[y]]=a;
		par[par[y]]=par[x];
	}
	else{
		weight[par[x]]=-a;
		par[par[x]]=par[y];
		if(r[par[x]]==r[par[y]])r[par[y]]++;
	}
	/*
	x=root(x);
	y=root(y);
	int a=w-(weight[y]-weight[x]);
	if(r[x]>r[y]){
		weight[y]=a;
		par[y]=x;
	}
	else{
		weight[x]=-a;
		par[x]=y;
		if(r[x]==r[y])r[y]++;
	}
	*/
}

int diff(int x,int y){
	return weight[y]-weight[x];
}


int main(){
	int n,q;
	cin>>n>>q;
	int qu;
	int x,y,z;
	init(n);
	for(int i=0;i<q;i++){
		cin>>qu;
		if(qu==0){
			cin>>x>>y>>z;
			unite(x,y,z);
		}
		else if(qu==1){
			cin>>x>>y;
			if(same(x,y)){
				cout<<diff(x,y)<<endl;
			}
			else{
				cout<<"?"<<endl;
			}
		}
	}

	
	return 0;
}