Graph decomposition

Consider an undirected graph $G$. An $r$-factor of $G$ is a subgraph that contains all vertices of $G$ and some subset of the edges of $G$, such that every vertex has degree $r$. Such a graph is called $r$-regular.

Let $G$ be a $k$-regular graph, and let $\lambda$ be a partition of $k$ into parts: $k = a_1 + a_2 + \ldots + a_m$. A $\lambda$-decomposition of $G$ is a set of graphs $G_1, G_2, \ldots, G_m$ such that each $G_i$ is an $a_i$-factor of $G$, and every edge of $G$ belongs to exactly one of the graphs $G_i$.

For the complete graph $K_{2n}$ with an even number of vertices and a partition $\lambda$ of $2n-1$ into parts, construct a $\lambda$-decomposition of $K_{2n}$.

The first line contains an integer $n$ ($1 \le n \le 100$). The second line contains an integer $m$, followed by the numbers $a_1, a_2, \ldots, a_m$ ($1 \le a_i \le 2n-1$, $\sum a_i = 2n-1$).

Print $m$ descriptions of graphs. The description of $G_i$ must contain $n a_i$ edges. Separate the graph descriptions with blank lines.