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>
using namespace std;
using UL = unsigned int;
using ULL = unsigned long long;
using LL = long long;
#define rep(i,n) for(UL i=0; i<(n); i++)

struct UF{
 UL N;
 vector<pair<UL,LL>> V;
 void init(UL n){
  N=n; V.resize(N);
  rep(i,N) V[i]={i,0};
 }
 pair<UL,LL> root(UL a){
  if(V[a].first==a) return V[a];
  auto buf=root(V[a].first);
  buf.second+=V[a].second;
  return V[a]=buf;
 }
 void unite(UL r,UL s,LL h){
  auto R=root(r); r=R.first; h+=R.second;
  R=root(s); s=R.first; h-=R.second;
  if(r==s) return;
  V[s]={r,h};
 }
};

bool PtrCmp(int* l, int* r) {return *l<*r;}

int main() {
 UL N,Q; scanf("%u%u",&N,&Q);
 UF G; G.init(N);
 rep(q,Q){
  UL c; scanf("%u",&c);
  if(c==0){
   UL x,y,h; scanf("%u%u%u",&x,&y,&h);
   G.unite(x,y,h);
  }
  else if(c==1){
   UL x,y; scanf("%u%u",&x,&y);
   auto X=G.root(x);
   auto Y=G.root(y);
   if(X.first!=Y.first) printf("?\n");
   else printf("%lld\n",Y.second-X.second);
  }
 }
 return 0;
}