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CSES Problem Set

Flight Routes Check

Task | Statistics

CSES - Flight Routes CheckCSES - Flight Routes Check

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 $b$.


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