#ifdef LOCAL
#pragma GCC optimize ("O0")
#else
#pragma GCC optimize ("O3")
#endif


#include <bits/stdc++.h>


using namespace std;

using ll = long long;
const int INF = 1e9 + 7;
const int MOD = INF;
const ll INF_LL = 1e18 + 7;

#define __overload3(_1, _2, _3, name,...) name
#define rep(...) __overload3(__VA_ARGS__, repFromUntil, repUntil, repeat)(__VA_ARGS__)
#define repeat(times) repFromUntil(__name, 0, times)
#define repUntil(name, times) repFromUntil(name, 0, times)
#define repFromUntil(name, from, until) for (int name = from, name##__until = (until); name < name##__until; name++)
#define repFromTo(name, from, to) repFromUntil(name, from, to + 1)
#define repr(...) __overload3(__VA_ARGS__, reprFromUntil, reprUntil, repeat)(__VA_ARGS__)
#define reprUntil(name, times) reprFromUntil(name, 0, times)
#define reprFromUntil(name, from, until) for (int name = until - 1, name##__from = (from); name >= name##__from; name--)
#define reprFromTo(name, from, to) reprFromUntil(name, from, to + 1)

#define debugos OUT
#ifdef LOCAL
#define debug(v) {printf("L%d %s > ",__LINE__,#v);debugos<<(v)<<newl;}
#define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:(v)){debugos<<e<<" ";}debugos<<newl;}
#define debuga(m,w) {printf("L%d %s > ",__LINE__,#m);for(int x=0;x<(w);x++){debugos<<(m)[x]<<" ";}debugos<<newl;}
#define debugaa(m,h,w) {printf("L%d %s >\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){debugos<<(m)[y][x]<<" ";}debugos<<newl;}}
#else
#define debug(v) {}
#define debugv(v) {}
#define debuga(m,w) {}
#define debugaa(m,h,w) {}
#endif

#define newl "\n"

#define all(iter) begin(iter), end(iter)


template <class T> bool chmin(T& var, T x) {
  if (var > x) {
    var = x;
    return true;
  } else return false;
}
template <class T> bool chmax(T& var, T x) {
  if (var < x) {
    var = x;
    return true;
  } else return false;
}

class MyScanner {
  public:
    template<typename T> void input_integer(T& var) {
        var = 0; T sign = 1;
        int cc = getchar();
        for (; cc<'0' || '9'<cc; cc = getchar())
            if (cc == '-') sign = -1;
        for (; '0' <= cc && cc <= '9'; cc = getchar())
            var = (var << 3) + (var << 1) + cc - '0';
        var = var * sign;
    }
    int c() { char c; while (c = getchar(), c == ' ' or c == '\n'); return c; }
    MyScanner& operator>>(char& var) { var = c(); return *this; }
    MyScanner& operator>>(int& var) { input_integer<int>(var); return *this; }
    MyScanner& operator>>(ll& var) { input_integer<ll>(var); return *this; }
    MyScanner& operator>>(string& var) {
        int cc = getchar();
        for (; !isvisiblechar(cc); cc = getchar());
        for (; isvisiblechar(cc); cc = getchar())
            var.push_back(cc);
        return *this;
    }
    operator int() {
      int n;
      *this >> n;
      return n;
    }
    operator ll() {
      ll n;
      *this >> n;
      return n;
    }
    private:
      int isvisiblechar(int c) {
        return 0x21 <= c && c <= 0x7E;
      }
};
class MyPrinter {
  public:
    template<typename T>
    void output_integer(T var) {
        if (var == 0) { putchar('0'); return; }
        if (var < 0)
            putchar('-'),
            var = -var;
        char stack[32]; int stack_p = 0;
        while (var)
            stack[stack_p++] = '0' + (var % 10),
            var /= 10;
        while (stack_p)
            putchar(stack[--stack_p]);
    }
    MyPrinter& operator<<(char c) { putchar(c); return *this; }
    template <typename T>
    MyPrinter& operator<<(T var) { output_integer<T>(var); return *this; }
    MyPrinter& operator<<(char* str_p) { while (*str_p) putchar(*(str_p++)); return *this; }
    MyPrinter& operator<<(const char* str_p) { while (*str_p) putchar(*(str_p++)); return *this; }
    MyPrinter& operator<<(const string& str) {
        const char* p = str.c_str();
        const char* l = p + str.size();
        while (p < l) putchar(*p++);
        return *this;
    }
    // MyPrinter& operator<<(const modint& var) { output_integer<ll>(var.value); return *this; }
    template <typename T>
    void operator()(T x) {
#ifdef LOCAL
        *this << "----- OUTPUT ----- > ";
#endif
        *this << x << newl;
    }
};
MyScanner IN;
MyPrinter OUT;


template <typename Iter>
void dump(Iter s, Iter t) {
#ifdef LOCAL
        OUT << "----- OUTPUT ----- > ";
#endif
  if (s == t) OUT << "\n";
  else {
    for (; s != t; s++) {
      OUT << *s << " \n"[next(s, 1) == t];
    }
  }
}


template <typename Weight = int>
class weighted_union_find {
  public:
    /// <param name="len">要素数</param>
    weighted_union_find(int len, Weight unity = 0) {
      parent = new int[len];
      depth = new int[len];
      diff_weight = new Weight[len];
      for (int i = 0; i < len; i++) parent[i] = i;
      memset(depth, 0, len);
      fill(diff_weight, diff_weight + len, unity);
    }
    /// 根を特定、経路を圧縮　あまり外部から使わない
    int root(int x) {
      if (parent[x] == x) return x;
      else {
        int r = root(parent[x]);
        diff_weight[x] += diff_weight[parent[x]];
        return parent[x] = r;
      }
      return parent[x] == x ? x :
             (parent[x] = root(parent[x]));
    }
    /// 2つの要素が同じ木に属すると宣言　wはx -> y
    void unite(int x, int y, Weight w) {
      // wをroot(x) -> root(y)のものに書き換え
      w += weight(x);
      w -= weight(y);

      x = root(x);
      y = root(y);
      if (x == y) return;
      if (depth[x] < depth[y]) swap(x, y), w *= -1;
      parent[y] = x;
      if (depth[x] == depth[y]) depth[x]++;
      diff_weight[y] = w;
    }
    /// 同じ木に属するか
    bool same(int x, int y) {
      return root(x) == root(y);
    }
    /// 重みを計算
    Weight weight(int x) {
      root(x);
      return diff_weight[x];
    }
    /// x -> y方向のweight差分
    /// xとyがsameか確認すること
    Weight diff(int x, int y) {
      return weight(y) - weight(x);
    }

  private:
    int *parent;
    int *depth;
    int *diff_weight;
};


int main() {
  int n, q; IN >> n >> q;
  weighted_union_find<> uf(n);

  int c, x, y, z;
  rep(q) {
    IN >> c >> x >> y;
    if (c == 0) {
      IN >> z;
      uf.unite(x, y, z);
    } else {
      OUT(uf.same(x, y) ? to_string(uf.diff(x, y)) : "?");
    }
  }
}


Measured memory_bytes: 4368