#include <bits/stdc++.h>
#define int long long int
#define MOD(x) ((x % MOD_N) + MOD_N) % MOD_N
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define FORE(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for(int i=(b)-1;i>=(a);--i)
#define RFORE(i,a,b) for(int i=(b);i>=(a);--i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(c) (c).begin(),(c).end()
#define RALL(c) (c).rbegin(),(c).rend()
#define SORT(c) sort(ALL(c))
#define RSORT(c) sort(RALL(c))
#define SZ(c) (int)((c).size())
#define EACH(i,v) for(auto i=v.begin();i!=v.end();++i)
#define REACH(i,v) for(auto i=v.rbegin();i!=v.rend();++i)
#define LB(c,x) distance((c).begin(),lower_bound(ALL(c),x))
#define UB(c,x) distance((c).begin(),upper_bound(ALL(c),x))
#define COUNT(c,x) (lower_bound(ALL(c),x)-upper_bound(ALL(c),x))
#define UNIQUE(c) SORT(c); (c).erase(unique(ALL(c)),(c).end());
#define COPY(c1,c2) copy(ALL(c1),(c2).begin())
#define EXIST(s,e) (bool)((s).find(e)!=(s).end())
#define PB push_back
#define MP make_pair
#define DUMP(x)  cerr<<#x<<" = "<<(x)<<endl;
#define NL cerr<<endl;
using namespace std;
template<typename T,typename U> using P=pair<T,U>;
template<typename T> using V=vector<T>;
template<typename T>bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<typename T>bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<typename T>T sum(vector<T>&v){return accumulate(ALL(v),T());}
template<typename T>T sum(vector<T>&v,int a,int b){return accumulate(v.begin()+a,v.begin()+b,T());}
template<typename T>T max(vector<T>&v){return *max_element(ALL(v));}
template<typename T>T min(vector<T>&v){return *max_element(ALL(v));}
template<typename T>T max_index(vector<T>&v){return distance((v).begin(),max_element(ALL(v)));}
template<typename T>T min_index(vector<T>&v){return distance((v).begin(),min_element(ALL(v)));}

struct edge { int to, cost; };

template<typename T>auto&operator<<(ostream&s,const vector<T>&v){s<<"[";bool a=1;for(auto e:v){s<<(a?"":" ")<<e;a=0;}s<<"]";return s;}
template<typename T,typename U>auto&operator<<(ostream&s,const pair<T,U>&p){s<<"("<<p.first<<","<<p.second<<")";return s;}
template<typename T>auto&operator<<(ostream&s,const set<T>&st){s<<"{";bool a=1;for(auto e:st){s<<(a?"":" ")<<e;a=0;}s<<"}";return s;}
template<typename T,typename U>auto&operator<<(ostream&s,const map<T,U>&m){s<<"{";bool a=1;for(auto e:m){s<<(a?"":" ")<<e.first<<":"<<e.second;a=0;}s<<"}";return s;}

const int INF = 1e18;
const int MOD_N = 1e9+7;

struct UnionFind
{
   vector<int> par, myrank;
   UnionFind(int n) {
      myrank.resize(n, 0);
      par.resize(n);
      for (int i = 0; i < n; i++) par[i] = i;
   }
   int root(int x) {
      if (par[x] == x) return x;
      return par[x] = root(par[x]);
   }
   bool merge(int x, int y) {
      x = root(x); y = root(y);
      if (x == y) return false;
      if (myrank[x] < myrank[y]) swap(x, y);
      par[y] = x;
      if(myrank[x] == myrank[y]) myrank[x]++;
      return true;
   }
   bool issame(int x, int y) {
      return root(x) == root(y);
   }
};
template<typename Abel>
struct WeightedUnionFind
{
   vector<int> par, myrank;
   vector<Abel> diff_weight;
   WeightedUnionFind(int n, Abel SUM_UNITY=0) {
      par.resize(n); myrank.resize(n, 0); diff_weight.resize(n);
      for (int i = 0; i < n; i++) { par[i] = i; diff_weight[i] = SUM_UNITY; }
   }
   int root(int x) {
      if (par[x] == x) return x;
      int r = root(par[x]);
      diff_weight[x] += diff_weight[par[x]];
      return par[x] = r;
   }
   Abel weight(int x) {
      root(x);
      return diff_weight[x];
   }
   Abel diff(int x, int y) {
      return weight(y) - weight(x);
   }
   bool merge(int x, int y, Abel w) {
      w += weight(x); w -= weight(y);
      x = root(x); y = root(y);
      if (x == y) return false;
      if (myrank[x] < myrank[y]) swap(x, y), w = -w;    
      par[y] = x;
      if(myrank[x] == myrank[y]) myrank[x]++;
      diff_weight[y] = w;
      return true;
   }
   bool issame(int x, int y) {
      return root(x) == root(y);
   }
};

signed main()
{
   int n, q; cin >> n >> q;
   V<int> c(q), x(q), y(q), z(q);
   REP(i, q) {
      cin >> c[i];
      if (c[i] == 0) {
         cin >> x[i] >> y[i] >> z[i];
      } else {
         cin >> x[i] >> y[i];
      }
   }
   WeightedUnionFind<int> wuf(n);
   REP(i, q) {
      if (c[i] == 0) {
         wuf.merge(x[i], y[i], z[i]);
      } else {
         if (wuf.issame(x[i], y[i])) {
            cout << wuf.diff(x[i], y[i]) << endl;
         } else {
            cout << "?" << endl;
         }
      }
   }

   return 0;
}



Measured memory_bytes: 11516