The directed unweighted graph is given. Find the lexicographically smallest topological ordering of its vertices. \InputFile The first line contains the number of vertices $n~(1 \le n \le 10^5)$ and the number of edges $m~(1 \le m \le 10^5)$ in a graph. Each of the next $m$ lines describes the edge of the graph --- two numbers, the initial and final vertex. \OutputFile Print the lexicographically smallest topological ordering of graph's vertices. If its impossible to sort graph topologically, print $-1$. \includegraphics{https://static.e-olymp.com/content/c8/c892750f0f88eb3a20f84a3344f54f2268287c3f.gif}