merged segment tree

void init(int node, int b, int e){
    if (b == e) {
        tree[node].push_back({sub[eu[b-1]], eu[b-1]});
        return;
    }
    int Left = node * 2;
    int Right = node * 2 + 1;
    int mid = (b + e) / 2;
    init(Left, b, mid);
    init(Right, mid + 1, e);
    tree[node].resize(tree[Right].size()+tree[Left].size());
    merge(tree[Left].begin(), tree[Left].end(), tree[Right].begin(), tree[Right].end(), tree[node].begin());
    //if(node==1) for(auto a: tree[node]) cout << a.se << " -> " << a.fi << endl;
}

pii query(int node, int b, int e, int i, int j, int num){
    if (i > e || j < b)
        return {inf, inf};
    if (b >= i && e <= j){
        pii t = {num, -1};
        int l = lower_bound(tree[node].begin(), tree[node].end(), t) - tree[node].begin();
        if(l == tree[node].size()) return {inf, inf};
        return tree[node][l];
    }
    int Left = node * 2;
    int Right = node * 2 + 1;
    int mid = (b + e) / 2;
    pii p1 = query(Left, b, mid, i, j, num);
    pii p2 = query(Right, mid + 1, e, i, j, num);
    return min(p1, p2);
}