#include <iostream>
#include <vector>
using namespace std;

class WeightedUnionFind {
public:
    vector<int> parents, rank, diff_weight;

    WeightedUnionFind(int n) : parents(n), rank(n), diff_weight(n) {
        for (int i = 0; i < n; i++) {
            parents[i] = i;
            rank[i] = 0;
            diff_weight[i] = 0;
        }        
    }

    int root(int x) {
        if (parents[x] == x) { // root
            return x;
        } else {
            int r = root(parents[x]);
            diff_weight[x] += diff_weight[parents[x]];
            return parents[x] = r;
        }
    }

    bool isSame(int x, int y) {
        return root(x) == root(y);
    }

    bool unite(int x, int y, int w) {
        w += weight(x); w -= weight(y);
        x = root(x); y = root(y);
        if (x == y) return false;

        if (rank[x] < rank[y]) {
            swap(x, y);
            w = -w;
        }

        if (rank[x] == rank[y]) ++rank[x];
        parents[y] = x;

        diff_weight[y] = w;

        return true;
    }

    int weight(int x) {
        root(x);
        return diff_weight[x];
    }

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

int main(void) {

    int n, q; cin >> n >> q;
    WeightedUnionFind wuf(n);

    for (int i = 0; i < q; i++) {
        int type; cin >> type;
        if (type == 0) {
            int x, y, z; cin >> x >> y >> z;            
            wuf.unite(x, y, z);
        } else if (type == 1) {
            int x, y; cin >> x >> y;
            if (!wuf.isSame(x, y)) cout << "?" << endl;
            else cout << wuf.diff(x, y) << endl;
        }
    }

    return 0;
}
