E. Tree Constructing
constructive algorithms; graphs
You are given three integers \(n\), \(d\) and \(k\).Your task is to construct an undirected tree on \(n\) vertices with diameter \(d\) and degree of each vertex at most \(k\), or say that it is impossible.An undirected tree is a connected undirected graph with \(n - 1\) edges.Diameter of a tree is the maximum length of a simple path (a path in which each vertex appears at most once) between all pairs of vertices of this tree.Degree of a vertex is the number of edges incident to this vertex (i.e. for a vertex \(u\) it is the number of edges \((u, v)\) that belong to the tree, where \(v\) is any other vertex of a tree).
The first line of the input contains three integers \(n\), \(d\) and \(k\) (\(1 \le n, d, k \le 4 \cdot 10^5\)).
If there is no tree satisfying the conditions above, print only one word ""NO"" (without quotes).Otherwise in the first line print ""YES"" (without quotes), and then print \(n - 1\) lines describing edges of a tree satisfying the conditions above. Vertices of the tree must be numbered from \(1\) to \(n\). You can print edges and vertices connected by an edge in any order. If there are multiple answers, print any of them.1