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 <algorithm>
#include <vector>
#include <map>
#include <queue>
#include <utility>
#include <iomanip>
#include <cmath>
using namespace std;
#define REP(i,n) for (int i=0;i<(n);++i)
#define rep(i,a,b) for(int i=a;i<(b);++i)
template<class T> inline bool chmin(T &a, T b){ if(a > b) { a = b; return true;} return false;}
template<class T> inline bool chmax(T &a, T b){ if(a < b) { a = b; return true;} return false;}
using ll = long long;
constexpr ll INF = 1LL << 60;
constexpr int MOD = 1e9 + 7;

struct UnionFind {
    vector<int> par, weight;
    UnionFind(int n) :par(n,-1), weight(n) {}
    void unite(int x, int y, int w = 0) {
        w += get_weight(x); w -= get_weight(y);
        x = root(x); y = root(y);
        if (x == y) return;
        if (par[x] > par[y]) swap(x, y), w = -w;
        par[x] += par[y];
        par[y] = x;
        weight[y] = w;
        return;
    }
    bool same(int x, int y) { return root(x) == root(y); }
    int root(int x) {
        if(par[x] < 0) return x;
        int r = root(par[x]);
        weight[x] += get_weight(par[x]);
        return par[x] = r;
    }
    int sizeOf(int x) { return -par[root(x)]; }
    int get_weight(int x) { root(x); return weight[x]; }
    int diff(int x, int y) { return get_weight(y) - get_weight(x); }
};

int main() {
    cin.tie(0); ios_base::sync_with_stdio(false);
    int N,M;cin>>N>>M;
    UnionFind uf(N);
    int L,R,D,A;
    for(int i=0;i<M;++i){
        cin>>A>>L>>R;
        if(A==0){
            cin>>D;
            uf.unite(L,R,D);
        } else {
            if(uf.same(L,R)){
                cout << uf.diff(L,R) << '\n';
            } else {
                cout << '?' << '\n';
            }
        }
    }
    return 0;
}