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;

int par[101010];
int diff[101010];

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

int weight(int x) {
    find(x);
    return diff[x];
}

void unite(int x, int y, int w) {
    w += weight(x);
    w -= weight(y);
    x = find(x);
    y = find(y);
    par[y] = x;
    diff[y] = w;
}

int main() {
    int n, q;
    cin >> n >> q;
    for (int i = 0; i < n; i++) {
        par[i] = i;
    }
    while (q--) {
        int t;
        cin >> t;
        if (t == 0) {
            int x, y, w;
            cin >> x >> y >> w;
            unite(x, y, w);
        } else {
            int x, y;
            cin >> x >> y;
            if (find(x) == find(y)) {
                cout << weight(y) - weight(x) << endl;
            } else {
                cout << "?" << endl;
            }
        }
    }
}