Topological sort

We must perform $n$ tasks, one at a time. Furthermore, some tasks must be done before others: there are $m$ precedence relations between tasks. Write a program to print a way to sort the $n$ tasks satisfying the $m$ given precedences.

Input

Input consists of several cases. Every case begins with $n$ , followed by $m$ , followed by $m$ distinct pairs $x$ $y$ that indicate that task $x$ must be done before task $y$ . You can assume $1 \le n \le 10^4$ , $0 \le m \le 10n$ , and that the tasks are numbered from 0 to $n - 1$ .

Output

For every case, print the lexicographically smallest order of the $n$ tasks that fulfills the $m$ given precedences. There will always be, at least, one solution.

Problem information

Author: Unknown
Translator: Salvador Roura

Generation: 2026-01-25T10:10:32.072Z