7586: [CSES Problem Set] Flight Routes Check
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Description
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.
Input
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.
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.
Output
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 $b$. If there are several possible solutions, you can print any of them.
In the latter case also print two cities $a$ and $b$ such that you cannot travel from city $a$ to city $b$. If there are several possible solutions, you can print any of them.
Constraints
$1≤n≤10^5$
$1 \le m \le 2 \cdot 10^5$
$1 \le a,b \le n$
$1 \le m \le 2 \cdot 10^5$
$1 \le a,b \le n$
Sample 1 Input
4 5
1 2
2 3
3 1
1 4
3 4
Sample 1 Output
NO
4 2