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>
using namespace std;

int par[111111];
int rnk[111111];
int W[111111];

int root(int x){
  if(par[x]==x) return x;
  root(par[x]);
  W[x]+=W[par[x]];
  return par[x]=root(par[x]);
}

int weight(int x){
  root(x);
  return W[x];
}

void unite(int x,int y,int w){
  w+=weight(x);
  w-=weight(y);
  x=root(x);
  y=root(y);
  if(x==y) return;
  if(rnk[x]<rnk[y]) swap(x,y), w=-w;
  rnk[x]+=rnk[y];
  par[y]=x;
  W[y]=w;
}

signed main(){
  for(int i=0;i<111111;i++)par[i]=i;
  int n,m;
  cin>>n>>m;
  while(m--){
    int a,b,c,d;
    cin>>a>>b>>c;
    if(a==1){
      if(root(b)==root(c)){
        cout<< weight(c) - weight(b) <<endl;
      }
      else cout<<"?"<<endl;
    }
    else{
      cin>>d;
      unite(b,c,d);
    }
  }

}