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<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<iomanip>
#include<math.h>
#include<complex>
#include<queue>
#include<deque>
#include<map>
#include<set>
#include<bitset>
using namespace std;
#define REP(i,m,n) for(int i=(int)m ; i < (int) n ; i++ )
#define rep(i,n) REP(i,0,n)
typedef long long ll;
typedef pair<int,int> pint;
typedef pair<ll,int> pli;
const int inf=1e9+7;
const ll longinf=1LL<<60 ;
const ll mod=1e9+7 ;
int dx[4]={1,0,-1,0} , dy[4]={0,1,0,-1} ;
struct pUF{
    vector<ll> r, par;
    pUF(int n):r(n),par(n,-1){};

    int find(int x){
       if(par[x]<0)
           return x;
       int y = find(par[x]);
       r[x] += r[par[x]];
       return par[x] = y;
    }

    bool same(int x,int y){
        return find(x)==find(y);
    }
    
    ll weight(int x){
       find(x);
       return r[x];
    }

    ll diff(int x,int y){//weigth(y)-weight(x)を出力
        return weight(y)-weight(x);
    }
    
    bool unite(ll c,int x, int y){//weight(y)-weight(x)=cとなるようにつなぐ
        c -= weight(y);
        c += weight(x);
        x = find(x);
        y = find(y);
        if(x!=y){
           par[y] = x;
           r[y] = c;
           return true;
       }
       return false;
    }
};
int main(){
    int n;
    cin>>n;
    pUF uf(n);
    int q;
    cin>>q;
    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(z,x,y);
        }
    }


   return 0;
}