Competitions

# Topological sort

# Topological Sort

The directed unweighted graph is given. Sort topologically its vertices.

#### Input

The first line contains the number of vertices **n** (**1** ≤ **n** ≤ `10`

) and the number of edges ^{5}**m** (**1** ≤ **m** ≤ `10`

) in a graph. Each of the next ^{5}**m** lines describes the edge of the graph - two numbers, the initial and final vertex.

#### Output

Sort the graph topologically and print its sequence of vertices. If its impossible to sort graph topologically, print **-1**.

Input example #1

6 6 1 2 3 2 4 2 2 5 6 5 4 6

Output example #1

4 6 3 1 2 5