{"raw_statement":[{"iden":"problem statement","content":"In Takahashi Kingdom, there is an archipelago of $N$ islands, called Takahashi Islands. For convenience, we will call them Island $1$, Island $2$, ..., Island $N$.\nThere are $M$ kinds of regular boat services between these islands. Each service connects two islands. The $i$\\-th service connects Island $a_i$ and Island $b_i$.\nCat Snuke is on Island $1$ now, and wants to go to Island $N$. However, it turned out that there is no boat service from Island $1$ to Island $N$, so he wants to know whether it is possible to go to Island $N$ by using two boat services.\nHelp him."},{"iden":"constraints","content":"*   $3 ≤ N ≤ 200$ $000$\n*   $1 ≤ M ≤ 200$ $000$\n*   $1 ≤ a_i < b_i ≤ N$\n*   $(a_i, b_i) \\neq (1, N)$\n*   If $i \\neq j$, $(a_i, b_i) \\neq (a_j, b_j)$."},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$N$ $M$\n$a_1$ $b_1$\n$a_2$ $b_2$\n:\n$a_M$ $b_M$"},{"iden":"sample input 1","content":"3 2\n1 2\n2 3"},{"iden":"sample output 1","content":"POSSIBLE"},{"iden":"sample input 2","content":"4 3\n1 2\n2 3\n3 4"},{"iden":"sample output 2","content":"IMPOSSIBLE\n\nYou have to use three boat services to get to Island $4$."},{"iden":"sample input 3","content":"100000 1\n1 99999"},{"iden":"sample output 3","content":"IMPOSSIBLE"},{"iden":"sample input 4","content":"5 5\n1 3\n4 5\n2 3\n2 4\n1 4"},{"iden":"sample output 4","content":"POSSIBLE\n\nYou can get to Island $5$ by using two boat services: Island $1$ -> Island $4$ -> Island $5$."}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}