// includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(st, itr) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define vrep(v, i) for(int i = 0; i < (v).size(); i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
#define dump(a, n) for(int i = 0; i < n; i++)cout << a[i] << "\n "[i + 1 != n];
#define dump2(a, n, m) for(int i = 0; i < n; i++)for(int j = 0; j < m; j++)cout << a[i][j] << "\n "[j + 1 != m];
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
typedef complex<double> cd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;

// solve
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> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}

template <typename T>
struct WeightedUnionFind_{
  int n;
  vector<int> par;
  vector<int> rank;
  vector<T> diff_weight;
  WeightedUnionFind_(int n, T def=0): n(n){
    par.resize(n);
    rank.resize(n);
    diff_weight.resize(n);
    for(int i = 0; i < n; i++){
      par[i] = i;
      rank[i] = 0;
      diff_weight[i] = def;
    }
  }
  int find(int x){
    if(par[x] == x)return x;
    int r = find(par[x]);
    diff_weight[x] += diff_weight[par[x]];
    return par[x] = r;
  }
  T weight(int x){
    find(x);
    return diff_weight[x];
  }
  bool same(int x, int y){
    return find(x) == find(y);
  }
  bool unite(int x, int y, T w){
    w += weight(x), w -= weight(y);
    x = find(x), y = find(y);
    if(x == y)return false;
    if(rank[x] < rank[y])swap(x, y), w = - w;
    if(rank[x] == rank[y])rank[x]++;
    par[y] = x;
    diff_weight[y] = w;
    return true;
  }
  T diff(int x, int y){
    return weight(y) - weight(x);
  }
};

using WeightedUnionFind = WeightedUnionFind_<int>;

int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n, q;
  cin >> n >> q;
  WeightedUnionFind_<ll> wuf(n);
  rep(i, q){
    int c;
    cin >> c;
    if(c == 0){
      int x, y, z;
      cin >> x >> y >> z;
      wuf.unite(x, y, z);
    }else{
      int x, y;
      cin >> x >> y;
      if(wuf.same(x, y))cout << wuf.diff(x, y) << endl;
      else cout << '?' << endl;
    }
  }
  return 0;
}



Measured memory_bytes: 4408