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:
//
// Created by jal on 2019-10-08.
//

#include <bits/stdc++.h>
using namespace std;
const int N = 100001;
int F[N], W[N];
struct Info{
    int father, weight;
    Info(int father, int weight):father(father), weight(weight){}
};
Info getInfo(int x){
    if(x == F[x]){
        return Info(x, 0);
    }
    Info info_x = getInfo(F[x]);
    F[x] = info_x.father;
    W[x] += info_x.weight;
    return Info(F[x], W[x]);
}
void unite(int x, int y, int z){
    Info info_x = getInfo(x), info_y = getInfo(y);
    if(info_x.father == info_y.father)return;
    F[info_y.father] = info_x.father;
    W[info_y.father] = W[x] - W[y] + z;
}
int main(){
    int n, q;
    scanf("%d %d", &n, &q);
    for(int i = 0; i < n; i++){
        F[i] = i;
    }
    for(int i = 0; i < q; i++){
        int com, x, y, z;
        scanf("%d", &com);
        if(com == 0){
            scanf("%d %d %d", &x, &y, &z);
            unite(x, y, z);
        }else{
            scanf("%d %d", &x, &y);
            Info info_x = getInfo(x), info_y = getInfo(y);
            if(info_x.father == info_y.father){
                printf("%d\n", info_y.weight - info_x.weight);
            }else{
                printf("?\n");
            }
        }
    }
    return 0;
}