B. Pairstime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard outputToad Ivan has m pairs of integers, each integer is between 1 and n, inclusive. The pairs are (a_1, b_1), (a_2, b_2), \ldots, (a_m, b_m). He asks you to check if there exist two integers x and y (1 \leq x < y \leq n) such that in each given pair at least one integer is equal to x or y.InputThe first line contains two space-separated integers n and m (2 \leq n \leq 300\,000, 1 \leq m \leq 300\,000) — the upper bound on the values of integers in the pairs, and the number of given pairs.The next m lines contain two integers each, the i-th of them contains two space-separated integers a_i and b_i (1 \leq a_i, b_i \leq n, a_i \neq b_i) — the integers in the i-th pair.OutputOutput "YES" if there exist two integers x and y (1 \leq x < y \leq n) such that in each given pair at least one integer is equal to x or y. Otherwise, print "NO". You can print each letter in any case (upper or lower).ExamplesInput
4 6
1 2
1 3
1 4
2 3
2 4
3 4
Output
NO
Input
5 4
1 2
2 3
3 4
4 5
Output
YES
Input
300000 5
1 2
1 2
1 2
1 2
1 2
Output
YES
NoteIn the first example, you can't choose any x, y because for each such pair you can find a given pair where both numbers are different from chosen integers.In the second example, you can choose x=2 and y=4.In the third example, you can choose x=1 and y=2.
4 6
1 2
1 3
1 4
2 3
2 4
3 4

NO 
['graphs', 'implementation', '*1500']