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>
#include<algorithm>
#include<string>
#include<map>
#define _USE_MATH_DEFINES
#include<math.h>
#include<queue>
#include<deque>
#include<stack>
#include<cstdio>
#include<utility>
#include<set>
#include<list>
#include<cmath>
#include<stdio.h>
#include<string.h>
#include<iomanip>
#include<cstdio>
#include<cstdlib>
#include<cstring>
using namespace std;
#define FOR(i, a, b) for (ll i = (a); i <= (b); i++)
#define REP(i, n) FOR(i, 0, n - 1)
#define NREP(i, n) FOR(i, 1, n)
using ll = long long;
using pii = pair<int, int>;
using piii = pair<pii, pii>;
const ll dx[4] = { 0,1,0,-1 };
const ll dy[4] = { -1, 0, 1,0 };
const ll INF = 1e9 + 7;
int gcd(int x, int y) {
	if (x < y)swap(x, y);
	if (y == 0)return x;
	return gcd(y, x%y);
}
void mul(ll a, ll b) {
	a = a * b % INF;
}
double mysqrt(double x) {
	double l = 0, r = x;
	for (int i = 0; i < 64; ++i) {
		double m = (l + r) / 2.0;
		if (m*m < x)l = m;
		else r = m;
	}
	return l;
}
///////////////////////////////////////

template<class Abel> struct UnionFind {
	vector<int> par;
	vector<int> rank;
	vector<Abel> diff_weight;

	UnionFind(int n = 1, Abel SUM_UNITY = 0) {
		init(n, SUM_UNITY);
	}

	void init(int n = 1, Abel SUM_UNITY = 0) {
		par.resize(n); rank.resize(n); diff_weight.resize(n);
		for (int i = 0; i < n; ++i) par[i] = i, rank[i] = 0, diff_weight[i] = SUM_UNITY;
	}

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

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

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

	bool merge(int x, int y, Abel 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;
	}

	Abel diff(int x, int y) {
		return weight(y) - weight(x);
	}
};
int main() {
	UnionFind<int> tree(1000100);
	int n, q; cin >> n >> q;
	REP(i, q) {
		int x; cin >> x;
		if (x) {
			int X, Y; cin >> X >> Y;
			if (!tree.issame(X, Y)) {
				cout << '?' << endl;
			}
			else {
				cout << tree.diff(Y, X) << endl;
			}
		}
		else {
			int X, Y, Z; cin >> X >> Y >> Z;
			tree.merge(Y,X,Z);
		}
	}
	return 0;
}