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<climits>
#include<cmath>
#include<iomanip>
#include<iostream>
#include<list>
#include<map>
#include<numeric>
#include<queue>
#include<set>
#include<stack>
#include<utility>
#include<vector>

using namespace std;

#define lint long long
#define REP(i, x, n) for(int i = x ; i < n ; i++)
#define rep(i, n) REP(i, 0, n)
#define repr(i, n) for(int i = n - 1 ; i >= 0 ; i--)
#define SORT(c) sort((c).begin(), (c).end())
#define SORT_INV(c) sort((c).begin(), (c).end(), greater<int>())
#define IINF (int)(1e9+10)
#define LLINF (lint)(1e18+10)

struct weightedUnionFind{

    vector<int> par, rank, wei;

    void init(int n){
        par.resize(n);
        rank.resize(n, 0);
        wei.resize(n, 0);
        rep(i, n){
            par[i] = i;
        }
        return;
    }

    int root(int x){
        if(par[x] == x){
            return x;
        }else{
            int r = root(par[x]);
            wei[x] += wei[par[x]];
            return par[x] = r;
        }
    }

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

    bool same(int x, int y){
        return root(x) == root(y);
    }

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

    int diff(int x, int y){
        return weight(x) - weight(y);
    }

};

int main(){
    int n, q;
    cin >> n >> q;
    weightedUnionFind wuf;
    wuf.init(n);
    rep(i, q){
        int query;
        cin >> query;
        if(query == 0){
            int x, y, z;
            cin >> x >> y >> z;
            wuf.unite(x, y, z);
        }else if(query == 1){
            int x, y;
            cin >> x >> y;
            if(wuf.same(x, y)){
                cout << wuf.diff(x, y) << endl;
            }else{
                cout << "?" << endl;
            }
        }
    }
    return 0;
}