#include "bits/stdc++.h"

// Begin Header {{{
using namespace std;

#ifndef DEBUG
#define dump(...)
#endif

#define all(x) x.begin(), x.end()
#define rep(i, n) for (intmax_t i = 0, i##_limit = (n); i < i##_limit; ++i)
#define reps(i, b, e) for (intmax_t i = (b), i##_limit = (e); i <= i##_limit; ++i)
#define repr(i, b, e) for (intmax_t i = (b), i##_limit = (e); i >= i##_limit; --i)
#define var(Type, ...) Type __VA_ARGS__; input(__VA_ARGS__)

constexpr size_t    operator""_zu(unsigned long long value) { return value; };
constexpr intmax_t  operator""_jd(unsigned long long value) { return value; };
constexpr uintmax_t operator""_ju(unsigned long long value) { return value; };

constexpr int INF = 0x3f3f3f3f;
constexpr intmax_t LINF = 0x3f3f3f3f3f3f3f3f_jd;

template <class T>
using MaxHeap = priority_queue<T, vector<T>, less<T>>;
template <class T>
using MinHeap = priority_queue<T, vector<T>, greater<T>>;

inline void input() {}
template <class Head, class... Tail>
inline void input(Head&& head, Tail&&... tail) {
    cin >> head;
    input(forward<Tail>(tail)...);
}

template <class T>
inline void input(vector<T> &vec) {
    for (auto &e: vec) {
        cin >> e;
    }
}

template <class T>
inline void input(vector<vector<T>> &mat) {
    for (auto &vec: mat) {
        input(vec);
    }
}

inline void print() { cout << "\n"; }
template <class Head, class... Tail>
inline void print(Head&& head, Tail&&... tail) {
    cout << head;
    if (sizeof...(tail)) cout << " ";
    print(forward<Tail>(tail)...);
}

template <class T>
inline ostream& operator<<(ostream &strm, const vector<T> &vec) {
    static constexpr const char *delim[] = {" ", ""};
    for (const auto &e: vec) {
        strm << e << delim[&e == &vec.back()];
    }
    return strm;
}

template <class T>
inline vector<T> make_v(const T &initValue, size_t sz) {
    return vector<T>(sz, initValue);
}

template <class T, class... Args>
inline auto make_v(const T &initValue, size_t sz, Args... args) {
    return vector<decltype(make_v<T>(initValue, args...))>(sz, make_v<T>(initValue, args...));
}

template <class Func>
class FixPoint : Func {
public:
    explicit constexpr FixPoint(Func&& f) noexcept : Func(forward<Func>(f)) {}

    template <class... Args>
    constexpr decltype(auto) operator()(Args&&... args) const {
        return Func::operator()(*this, std::forward<Args>(args)...);
    }
};

template <class Func>
static inline constexpr decltype(auto) makeFixPoint(Func&& f) noexcept {
    return FixPoint<Func>{forward<Func>(f)};
}

template <class T>
inline bool chmax(T &a, const T &b) noexcept {
    return b > a && (a = b, true);
}

template <class T>
inline bool chmin(T &a, const T &b) noexcept {
    return b < a && (a = b, true);
}

template <class T>
inline T diff(const T &a, const T &b) noexcept {
    return a < b ? b - a : a - b;
}
// End Header }}}

// WeightedUnionFind {{{
template <class Abel>
struct WeightedUnionFind {
    vector<int> tree;
    vector<Abel> diffWeight;

    explicit WeightedUnionFind(const size_t n, Abel SUM_UNITY = 0) :
        tree(n + 1, -1), diffWeight(n + 1, SUM_UNITY)
    {}

    size_t size(size_t x) {
        return -tree[root(x)];
    }

    size_t root(size_t x) {
        if (tree[x] < 0) {
            return x;
        } else {
            const size_t r = root(tree[x]);
            diffWeight[x] += diffWeight[tree[x]];
            return tree[x] = r;
        }
    }

    Abel weight(size_t x) {
        root(x);
        return diffWeight[x];
    }

    Abel diff(size_t x, size_t y) {
        return weight(y) - weight(x);
    }

    bool connected(size_t x, size_t y) {
        return root(x) == root(y);
    }

    bool unite(size_t x, size_t y, Abel w) {
        w += weight(x);
        w -= weight(y);
        x = root(x);
        y = root(y);
        if (x == y) {
            return false;
        }
        tree[x] += tree[y];
        tree[y] = x;
        diffWeight[y] = w;
        return true;
    }
};
// }}}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    var(size_t, N, Q);

    WeightedUnionFind<intmax_t> uf(N);
    while (Q--) {
        var(size_t, query);
        if (query == 0) {
            var(size_t, x, y);
            var(intmax_t, z);
            uf.unite(x, y, z);
        } else {
            var(size_t, x, y);
            if (!uf.connected(x, y)) {
                print('?');
            } else {
                print(uf.diff(x, y));
            }
        }
    }

    return 0;
}



Measured memory_bytes: 4156