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 <bits/stdc++.h>
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define eps LDBL_EPSILON
#define moder 1000000007
#define int long long
#define ll long long
#define INF LLONG_MAX/3
#define P std::pair<int,int>
#define prique priority_queue<int,vector<int>,greater<int>>
using namespace std;
int par[100010],ran[100010],dw[100010];
void init(){
	rep(i,100010){
		par[i]=i;
		ran[i]=0;
		dw[i]=0;
	}
}
int find(int x){
	if(par[x]==x)return x;
	else{
		int r=find(par[x]);
		dw[x]+=dw[par[x]];
		return par[x]=r;
	}
}
int weight(int x){
	find(x);
	return dw[x];
}
void unite(int x,int y,int w){
	w+=weight(x);
	w-=weight(y);
	x=find(x);
	y=find(y);
	if(x==y)return;
	if(ran[x]<ran[y]){
		par[x]=y;
		dw[x]=-w;
	}
	else{
		par[y]=x;
		dw[y]=w;
		if(ran[x]==ran[y])ran[x]++;
	}
}
bool same(int a,int b){
	return find(a)==find(b);
}
int diff(int x,int y){
	return weight(y)-weight(x);
}
int n,q;
int com,x,y,z;
signed main(){
	cin>>n>>q;
	init();
	rep(i,q){
		cin>>com;
		if(com==0){
			cin>>x>>y>>z;
			unite(x,y,z);
		}
		else{
			cin>>x>>y;
			if(!same(x,y))cout<<"?"<<endl;
			else cout<<diff(x,y)<<endl;
		}
	}
	return 0;
}