Flight routes check

Input

The first line contains two integers $n$ and $m$ — the number of cities and flights. The cities are numbered with integers 1, 2, \ldots, n.

The next $m$ lines describe the flights. Each line contains two integers $a$ and $b$, meaning that there is a flight from city $a$ to city $b$. All flights are one-way.

Output

Print "YES" if all routes are possible, and "NO" otherwise. In the latter case, also print two cities $a$ and $b$ such that it is impossible to travel from $a$ to $b$.

Examples