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;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())

template<class T>
struct WeightedUnionFind {
private:
    vector<int> par, rank;
    vector<T> diff_weight;
    
public:
    WeightedUnionFind() {}
    WeightedUnionFind(int n, T def = 0) {
        par.resize(n, -1);
        rank.resize(n, 0);
        diff_weight.resize(n, def);
    }
    
    int root(int x) {
        if (par[x] < 0) return x;
        int r = root(par[x]);
        diff_weight[x] += diff_weight[par[x]];
        return par[x] = r;
    }
    
    T weight(int x) {
        root(x);
        return diff_weight[x];
    }
    
    bool is_same(int x, int y) {
        return root(x) == root(y);
    }
    
    bool merge(int x, int y, T 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;
    }
    
    T diff(int x, int y) {
        return weight(y) - weight(x);
    }
    
    int size(int x) {
        return -par[root(x)];
    }
};

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    ll n, q;
    cin >> n >> q;
    WeightedUnionFind<ll> wuf(n);
    rep(i, q) {
        ll t;
        cin >> t;
        if (t == 0) {
            ll x, y, z;
            cin >> x >> y >> z;
            wuf.merge(x, y, z);
        }
        else {
            ll x, y;
            cin >> x >> y;
            if (wuf.root(x) == wuf.root(y)) {
                cout << wuf.diff(x, y) << endl;
            }
            else {
                cout << "?" << endl;
            }
        }
    }
    return 0;
}