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>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repr(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, m, n) for (int i = (m); i < (n); ++i)
#define FORR(i, m, n) for (int i = (m); i >= (n); --i)
#define equals(a, b) (fabs((a) - (b)) < EPS)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
//const ll mod = 1000000007;
//const ll mod = 998244353;
const int inf = 1e9 + 10;
const ll INF = 1e18;
const ld EPS = 1e-10;
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }

template<typename T>
class UnionFind {
public:
  vector<int> par, siz;
  vector<T> diff_weight;
    
  UnionFind(int sz_, T x) {
    init(sz_, x);
  }
  void init(int sz_, T x) {
    par.resize(sz_);
    siz.resize(sz_, 1);
    diff_weight.resize(sz_);
    rep(i, sz_) par[i] = i, diff_weight[i] = x;
  }

  int root(int x) { 
    if (par[x] == x) return x;
    else {
      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 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 (siz[x] < siz[y]) swap(x, y), w = -w;
    siz[x] += siz[y];
    par[y] = x;
    diff_weight[y] = w;
    return true;
  }

  bool issame(int x, int y) {
    return root(x) == root(y);
  }

  int size(int x) {
    return siz[root(x)];
  }

  T diff(int x, int y) {
    return weight(y) - weight(x);
  }
};

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout << fixed << setprecision(25);

  int n, q;
  cin >> n >> q;
  UnionFind<int> uf(n, 0);
  while (q--) {
    int c, x, y;
    cin >> c >> x >> y;

    if (c) {
      if (uf.issame(x, y)) cout << uf.diff(x, y) << '\n';
      else cout << "?\n";
    }
    else {
      int z;
      cin >> z;
      uf.merge(x, y, z);
    }
  }

  
  return 0;
}