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:
// clang-format off
#include <bits/stdc++.h>
using namespace std;
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
template<typename T = int> T in() { T x; cin >> x; return x; }
template<typename T = int> T in(T &&x) { T z(forward<T>(x)); cin >> z; return z; }
template<typename T> istream &operator>>(istream &is, vector<T> &v) { for (T &x : v) is >> x; return is; }
// clang-format on

template<typename CommutativeGroup> class WeightedUnionFind {
  using T = typename CommutativeGroup::value_type;
  CommutativeGroup g;

  vector<int> tree, rank;
  vector<T> diffWeight;

public:
  WeightedUnionFind(const int &n) : tree(n), rank(n), diffWeight(n, g.id()) { iota(all(tree), 0); }

  int root(const int &x) {
    if (tree[x] == x) {
      return x;
    } else {
      int r = root(tree[x]);
      diffWeight[x] += diffWeight[tree[x]];
      return tree[x] = r;
    }
  }

  T weight(const int &x) {
    root(x);
    return diffWeight[x];
  }

  bool same(const int &a, const int &b) { return root(a) == root(b); }

  bool unite(int a, int b, T w) {
    w = g(w, g(weight(a), g.inv(weight(b))));
    a = root(a), b = root(b);
    if (a == b) return false;
    if (rank[a] < rank[b]) swap(a, b), w = g.inv(w);
    tree[b] = a;
    diffWeight[b] = w;
    if (rank[a] == rank[b]) ++rank[a];
    return true;
  }

  T diff(int x, int y) { return g(weight(y), g.inv(weight(x))); }
};

template<typename T> struct sumGroup {
  using value_type = T;
  constexpr value_type id() { return 0; }
  constexpr value_type operator()(const value_type &a, const value_type &b) { return a + b; }
  constexpr value_type inv(const value_type &x) { return -x; }
};

int main() {
  int n = in();
  int q = in();
  WeightedUnionFind<sumGroup<int>> wuf(n);
  while (q--) {
    int c = in();
    if (c) {
      int x = in();
      int y = in();
      if (wuf.same(x, y)) {
        cout << wuf.diff(x, y) << endl;
      } else {
        cout << '?' << endl;
      }
    } else {
      int x, y, z;
      cin >> x >> y >> z;
      wuf.unite(x, y, z);
    }
  }
}