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>

#define MAXN 100000
typedef struct Values {
    int val;
    int comp;
} Values;

int main(){
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    Values a[MAXN];
    int n;
    int q;
    std::cin >> n;
    std::cin >> q;

    for(int i = 0; i < n; ++i){
        a[i].val = 0;
        a[i].comp = i;
    }
    for(int i = 0; i < q; ++i){
        int op;
        std::cin >> op;
        if(op == 0){
            //relate                                                                                                                                                                                                                
            int id1;
            int id2;
            int v;
            std::cin >> id1 >> id2 >> v;
            int v1 = 0;
            int v2 = 0;
            int i = id1;
            int j = id2;
            while(a[i].comp != i){
                v1 += a[i].val;
                i = a[i].comp;
            }
            while(a[j].comp != j){
                v2 += a[j].val;
                j = a[j].comp;
            }
            a[j].comp = i;
            a[j].val = v1 - v2 - v;
            a[id1].comp = i;
            a[id1].val = v1;
            a[id2].comp = i;
            a[id2].val = v1 - v;

       } else {
            int id1;
            int id2;
            std::cin >> id1 >> id2;
            int v1 = 0;
            int v2 = 0;
            while(a[id1].comp != id1){
                v1 -= a[id1].val;
                id1 = a[id1].comp;
            }
            while(a[id2].comp != id2){
                v2 -= a[id2].val;
                id2 = a[id2].comp;
            }

            if(id1 != id2) std::cout << "?\n";
            else std::cout << v2 - v1 << "\n";
        }
    }
    return 0;
}