h2. Restrictii

* $3 ≤ N ≤ 150$

* $3<=N<=150$

* $N ≤ M ≤ 5000$
h2. Exemplu

6 7
6 8
| 4

| In desen observam colorate cu verde muchiile unui arbore partial de diametru 4, acestea sunt: (1, 5), (2, 4), (3, 4), (4, 5), (4, 6), (5, 7), (6, 8)
!http://infoarena.ro/task/12perm?action=download&file=apdm.gif! |

| In desen observam colorate cu verde muchiile unui arbore partial de diametru 4, acestea sunt: (1, 5), (2, 4), (3, 4), (4, 5), (4, 6), (5, 7), (6, 8) |

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