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 <string.h>
#include <algorithm>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <cmath>
#include <stdio.h>
#include <vector>
#define int long long
#define endre getchar();getchar();return 0
#define moder 1000000007
#define inf 1000000000000000000
#define rep(i,n) for(int i=0;i<n;i++)
#define P pair<int,int>
#define all(v) v.begin(),v.end()
#define prique(T) priority_queue<T,vector<T>,greater<T>>
#define vecunique(vec) sort(vec.begin(), vec.end());decltype(vec)::iterator result = std::unique(vec.begin(), vec.end());vec.erase(result, vec.end())
using namespace std;

class weight_unionfind {
	int par[100005], Rank[100005], diff_weight[100005];
public:
	weight_unionfind(int x) {
		rep(i, x) {
			par[i] = i;
			Rank[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;
	}
	int weight(int x) {
		find(x);
		return diff_weight[x];
	}
	bool same(int x, int y) {
		return find(x) == find(y);
	}
	void unite(int x, int y, int w) {
		w += weight(x); w -= weight(y);
		x = find(x);
		y = find(y);
		if (x == y)return;
		if (Rank[x] < Rank[y])swap(x, y), w *= -1;
		if (Rank[x] == Rank[y])Rank[x]++;
		par[y] = x;
		diff_weight[y] = w;
	}
	int diff(int x, int y) {
		if (same(x, y))return weight(y) - weight(x);
		return inf;
	}
};
signed main() {
	int n, q;
	cin >> n >> q;
	static weight_unionfind uf(n);
	rep(i, q) {
		int a, b, c, d;
		cin >> a;
		if (!a) {
			cin >> b >> c >> d;
			uf.unite(b, c, d);
		}
		else {
			cin >> b >> c;
			if (uf.diff(b, c) != inf)cout << uf.diff(b, c) << endl;
			else cout << "?" << endl;
		}
	}
	endre;
}