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 loop(i,x,n) for(int i=(x);i<(n);i++)
#define all(v) (v).begin(),(v).end()
//#define int long long
using namespace std;
const int MOD=1e9+7;
const int INF=1e9;
template<typename T> void cmax(T &a, T b) {a = max(a, b);}
template<typename T> void cmin(T &a, T b) {a = min(a, b);}

template<typename Weight>class PotentializedUnionFind{
public:
  vector<int> par,rnk,sz;
  vector<Weight> difweight;
  PotentializedUnionFind(int n):
    par(n,-1),rnk(n,0),sz(n,1),difweight(n,0){}

  int find(int x){
    if(par[x]<0){return x;}
    else{
      int r=find(par[x]);
      difweight[x]+=difweight[par[x]];
      return par[x]=r;
    }
  }
  Weight weight(int x){
    find(x);
    return difweight[x];
  }
  bool same(int x,int y){return find(x)==find(y);}

  bool unite(int x,int y,Weight w){
    w+=weight(x);w-=weight(y);
    x=find(x);y=find(y);
    if(x==y)return false;
    if(rnk[x]<rnk[y])swap(x,y),w=-w;
    if(rnk[x]==rnk[y])rnk[x]++;
    par[y]=x;
    difweight[y]=w;
    return true;
  }
  Weight diff(int x,int y){return weight(y)-weight(x);}
};

int main(){
  int n,q;
  cin>>n>>q;
  PotentializedUnionFind<int> uf(n);
  rep(i,q){
    int t;
    cin>>t;
    if(t){
      int x,y;
      cin>>x>>y;
      if(uf.same(x,y)){
        cout<<uf.diff(x,y)<<endl;
      }else{
        cout<<"?"<<endl;
      }
    }else{
      int x,y,z;
      cin>>x>>y>>z;
      uf.unite(x,y,z);
    }
  }
 return 0;
}