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 <bits/stdc++.h>

using namespace std;
using ll = long long;

#define rep(i, a) for (int (i) = 0; (i) < (int) (a); (i)++)
#define reps(i, a, b) for (int (i) = (int) (a); (i) < (int) (b); (i)++)
#define rrep(i, a) for (int (i) = (int) a-1; (i) >= 0; (i)--)
#define rreps(i, a, b) for (int (i) = (int) (a)-1; (i) >= (int) (b); (i)--)
#define MP(a, b) make_pair((a), (b))
#define PB(a) push_back((a))
#define all(v) (v).begin(), (v).end()
#define PRINT(f) if((f)){cout << (TRUE__) << endl;}else{cout << FALSE__ << endl;}
#define TRUE__ "Yes"
#define FALSE__ "No"
#define PERM(v) next_permutation(all(v))
#define UNIQUE(v) sort(all(v));(v).erase(unique(all(v)), v.end())
#define CIN(type, x) type x;cin >> x

#ifdef LOCAL
#define lcout(a) cout << a;
#define lcoutln(a) cout << a << endl;
#define lcerr(a) cerr << a;
#define lcerrln(a) cerr << a << endl;
#else
#define lcout(a) 
#define lcoutln(a) 
#define lcerr(a) 
#define lcerrln(a) 
#endif

struct uni_find_weight
{
	vector<int> par;
	vector<int> rank;
	vector<int> diff_weight;
	int sz;
	uni_find_weight(int n) {init(n);}
	void init(int n) {
		par.resize(n);
		rank.resize(n);
		diff_weight.resize(n);
		rep(i, n) par[i] = i, rank[i] = 0, diff_weight[i] = 0;
		sz = n;
	}
	int root(int x) {
		if (par[x] == x) return x;
		int r = root(par[x]);
		diff_weight[x] += diff_weight[par[x]];
		return par[x] = r;
	}
	int weight(int x) {
		root(x);
		return diff_weight[x];
	}
	int diff(int x, int y) {return weight(y) - weight(x);}
	bool same(int x, int y) {return root(x) == root(y);}
	bool unite(int x, int y, int w) {
		w += weight(x);
		w -= weight(y);
		x = root(x);
		y = root(y);
		if (x == y) return false;
		if (rank[x] < rank[y]) swap(x, y), w = -w;
		if (rank[x] == rank[y]) rank[x]++;
		par[y] = x;
		diff_weight[y] = w;
		return true;
	}
	int size() {return sz;}
};

int main()
{
	int n, q;
	cin >> n >> q;
	uni_find_weight uf(n);
	rep(i, q) {
		CIN(int, t);
		CIN(int, a);
		CIN(int, b);
		if (t == 0) {
			CIN(int, w);
			uf.unite(a, b, w);
		}
		if (t == 1) {
			if (!uf.same(a, b)) cout << '?' << endl;
			else {
				cout << uf.diff(a, b) << endl;
			}
		}
	}
}