Competitions

# Topological sort

John has n tasks to do. Unfortunately, the tasks are not independent and the execution of one task is only possible if other tasks have already been executed.

#### Input

Consist of several instances of the problem. Each instance begins with a line containing two integers: number of tasks n (numbered from 1 to n, 1n100) and number m of direct precedence relations between tasks. After this, there will be m lines with two integers i and j, representing the fact that task i must be executed before task j.

An instance with n = m = 0 will finish the input.

#### Output

For each instance, print a line with n integers representing the tasks in a possible order of execution.

Time limit 1 second
Memory limit 128 MiB
Input example #1
6 6
1 2
3 2
4 2
2 5
6 5
4 6
3 1
3 2
0 0

Output example #1
3 1 4 2 6 5
1 3 2