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:
// I SELL YOU...! 
#include<iostream>
#include<vector>
#include<algorithm>
#include<functional>
#include<queue>
#include<chrono>
#include<iomanip>
#include<map>
#include<set>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
void init_io(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << setprecision(10);
}
class Wunion_find{
  int n;
  vector<int> par,rk,size,diff_w;
  public:
  Wunion_find(int max_n){
    n = max_n+1;
    for(int i=0;i<=n;i++){
      par.emplace_back(i);
      rk.emplace_back(0);
      size.emplace_back(1);
      diff_w.emplace_back(0);
    }
  }
  int root(int x){
    if(par[x]==x){
      return x;
    }
    int r = root(par[x]);
    diff_w[x] += diff_w[par[x]];
    return par[x] = r;
  }
  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(rk[x]<rk[y]){
      par[x] = y;
      size[y] += size[x];
      diff_w[x] = -w;
    }else{
      par[y] = x;
      if(rk[x]==rk[y]) rk[x]++;
      size[x] += size[y];
      diff_w[y] = w;
    }
  }
  bool same(int x,int y){
    return root(x)==root(y);
  }
  int weight(int x){
    root(x);
    return diff_w[x];
  }
  int diff(int x,int y){
    return weight(y)-weight(x);
  }
  int treesize(int x){
    return size[root(x)];
  }
};
signed main(){
  init_io();
  ll n,q,x,y,z,p;
  cin >> n>>q;
  Wunion_find wuf(n);
  for(int i=0;i<q;i++){
    cin >> p;
    if(p==0){
      cin >> x >> y >> z;
      wuf.unite(x,y,z);
    }else{
      cin >> x>> y;
      if(wuf.same(x,y)){
        cout << wuf.diff(x,y)<<endl;
      }else{
        cout <<"?\n";
      }
    }
  }
}