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 <vector>
using namespace std;

using ll = long long;
using vi = vector<int>;

#define for_(i,a,b) for(int i = (a);i < (b);i++)
#define rfor_(i,a,b) for(int i = (b)-1;i >= (a);i--)
#define rep(i,n) for_(i,0,(n))
#define rrep(i,n) rfor_(i,0,(n))

class WUF {
	private:
	vi par;
	vi dw;
	public:
	WUF() {}
	~WUF() {}
	void init(int n) {
		this->par.resize(n);
		this->dw.resize(n);
		for(int i=0;i<n;i++)this->par[i] = i, this->dw[i] = 0;
	}
	int root(int x) {
		if(this->par[x]==x)return x;
		else {
			int r = this->root(this->par[x]);
			this->dw[x] += this->dw[this->par[x]];
			return this->par[x] = r;
		}
	}
	bool same(int x, int y) {
		return this->root(x) == this->root(y);
	}
	int weight(int x) {
        this->root(x);
        return this->dw[x];
    }
	int diff(int x, int y) {
        return this->weight(y) - this->weight(x);
    }
	void unite(int x, int y, int z) {
        z -= this->diff(x, y);
        x = this->root(x);
        y = this->root(y);
		if(x == y)return ;
        this->par[y] = x;
        this->dw[y] = z;
	}
};

WUF a;

int main(){
	cin.tie(0);
	
	int n, q;
	cin>>n>>q;
	
	a.init(n);
	
	rep(i, q) {
		int c, x, y, z;
		cin>>c>>x>>y;
		if(c) {
			if(a.same(x, y))cout<<a.diff(x, y)<<endl;
			else cout<<'?'<<endl;
		} else {
			cin>>z;
			a.unite(x, y, z);
		}
	}

	return 0;
}