#pragma region templates
//C
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdalign>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif

using i8  = std::int8_t;
using i16 = std::int16_t;
using i32 = std::int32_t;
using i64 = std::int64_t;
using u8  = std::uint8_t;
using u16 = std::uint16_t;
using u32 = std::uint32_t;
using u64 = std::uint64_t;
using f32 = float;
using f64 = double;
using vi32  = std::vector<i32>;
using vu32  = std::vector<u32>;
using vi64  = std::vector<i64>;
using vu64  = std::vector<u64>;
using vvi32 = std::vector<vi32>;
using vvu32 = std::vector<vu32>;
using vvi64 = std::vector<vi64>;
using vvu64 = std::vector<vu64>;
using pi32  = std::pair<i32,i32>;
using pi64  = std::pair<i64,i64>;

#define FOR(i,a,b) for(i64 i=(a), i##_len=(b); i<i##_len; ++i)
#define REP(i,n) FOR(i,0,n)
#define REPS(i,n) for(i64 i=1LL; i<=static_cast<i64>(n); ++i)
#define RFOR(i,a,b) for(i64 i=(a), i##_len=(b); i>i##_len; --i)
#define RFORS(i,n) RFOR(i,n,0)

#define ALL(obj) (obj).begin(),(obj).end()
#define CLR(ar,val) memset(ar, val, sizeof(ar))
#define SZ(obj) (static_cast<i32>(obj.size()))
#define cauto const auto&
#define pb push_back
#define mp make_pair

const i32 dx[4]={1,0,-1,0};
const i32 dy[4]={0,1,0,-1};
const i32 INF32 = 0x3F3F3F3F;
const i64 INF64 = 0x3F3F3F3F3F3F3F3F;

template<class T> inline bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> inline bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

class range {
private:
    struct I {
        i32 x;
        i32 operator*() { return x; }
        bool operator!=(I& lhs) { return x<lhs.x; }
        void operator++() { ++x; }
    };
    I i,n;
public:
    explicit range(int n) : i({0}), n({n}) { }
    range(int i,int n) : i({i}), n({n}) { }
    I& begin() { return i; }
    I& end() { return n; }
};

struct IoSetup {
    IoSetup() {
        std::cin.tie(nullptr);
        std::ios::sync_with_stdio(false);
        std::cout << std::fixed << std::setprecision(10);
        std::cerr << std::fixed << std::setprecision(10);
    }
}iosetup;/// cin,coutを使うときは iosetup をここにつける

template<typename A, typename B> std::istream &operator>>(std::istream &is, std::pair<A, B> &p) { is >> p.first >> p.second;return is; }
template<typename A, typename B> std::ostream &operator<<(std::ostream &os, const std::pair<A, B>& p) { os << p.first << ' ' << p.second;return os; }
template<typename T> std::istream &operator>>(std::istream &is, std::vector<T> &v) { for(T& in : v) is >> in; return is; }
template<typename T> std::ostream &operator<<(std::ostream &os, const std::vector<T> &v) { for(i32 i = 0; i < SZ(v); i++) os << v[i] << (i+1 != SZ(v) ? " " : ""); return os; }
#pragma endregion

#pragma region UnionFind with Weight
template<typename T>
struct UFwW {
    vi32 data;
    std::vector<T> ws;

    UFwW() { }

    explicit UFwW(i32 sz) : data(sz, -1), ws(sz) { }

    i32 find(i32 k) {
        if (data[k] < 0) return k;
        auto par = find(data[k]);
        ws[k] += ws[data[k]];
        return (data[k] = par);
    }

    T weight(i32 t) {
        find(t);
        return ws[t];
    }

    bool unite(i32 x, i32 y, T w) {
        w += weight(x);
        w -= weight(y);
        x = find(x), y = find(y);
        if (x == y) return (false);
        if (data[x] > data[y]) {
            x ^= y ^= x ^= y;
            w *= -1;
        }
        data[x] += data[y];
        data[y] = x;
        ws[y] = w;
        return (true);
    }

    T diff(i32 x, i32 y) {
        return (weight(y) - weight(x));
    }
};
#pragma endregion

i32 main(){

    using namespace std;
    
    i32 N, M; cin >> N >> M;
    UFwW<i32> tree(N);
    while (M--) {
        i32 A, B, C, D;
        cin >> A >> B >> C;
        if (A == 0) {
            cin >> D;
            tree.unite(B, C, D);
        } else {
            if (tree.find(B) == tree.find(C)) {
                cout << tree.diff(B, C) << endl;
            }
            else {
                cout << "?" << endl;
            }
        }
    }

    return 0;
}


Measured memory_bytes: 3644