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 <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
#include <cstring>
#include <deque>
#include <iomanip>
#include <limits>
#include <fstream>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define CLR(mat) memset(mat, 0, sizeof(mat))
typedef long long ll;

// 重み付きUnion-Find
struct UnionFind {
  vector<int> par;
  vector<int> rnk;
  vector<int> diff_weight;
  int n;
  UnionFind(int n):n(n){
    par.resize(n);rnk.resize(n);diff_weight.resize(n);
    for(int i=0; i<n; i++){par[i] = i;rnk[i] = 0;diff_weight[i]=0;}
  }
  int find(int x){
      if(par[x] == x) return x;
      int r = find(par[x]);
      diff_weight[x] += diff_weight[par[x]];
      return par[x] = r;
  }
  // y - x = w
  bool unite(int x, int y, int 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;
      diff_weight[y] = w;
      return true;
  }
  bool isSame(int x, int y){return find(x) == find(y);}
  int weight(int x){
    find(x);
    return diff_weight[x];
  }
  int diff(int x, int y){
    return weight(y) - weight(x);
  }
};


int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n,q;
  cin>>n>>q;
  UnionFind UF(100005);
  FOR(i,0,q){
    int a;
    cin>>a;
    if(a==0){
      int x,y,z;
      cin>>x>>y>>z;
      UF.unite(x,y,z);
    } else {
      int x,y;
      cin >> x >> y;
      if(UF.isSame(x, y)) cout << UF.diff(x, y) << endl;
      else cout << "?" << endl;
    }
  }
  return 0;
}