Code Submission Evaluation System | Login |

**Task** | Statistics

Time limit: | 1.00 s | Memory limit: | 512 MB |

There are $n$ cities and $m$ flight connections. Your task is to check if you can travel from any city to any other city using the available flights.

The first input line has two integers $n$ and $m$: the number of cities and flights. The cities are numbered $1,2,\dots,n$.

After this, there are $m$ lines describing the flights. Each line has two integers $a$ and $b$: there is a flight from city $a$ to city $b$. All flights are one-way flights.

Print "YES" if all routes are possible, and "NO" otherwise. In the latter case also print two cities $a$ and $b$ such that you cannot travel from city $a$ to city $b$.

- $1 \le n \le 10^5$

- $1 \le m \le 2 \cdot 10^5$

- $1 \le a,b \le n$

Input:

`4 5`

1 2

2 3

3 1

1 4

3 4

Output:

`NO`

4 2