using System;
using System.Text;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
using static System.Math;

namespace NotFounds
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var sw = new System.IO.StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);
            new Program().Solve(new ConsoleInput(Console.In, ' '));
            Console.Out.Flush();
        }

        public void Solve(ConsoleInput cin)
        {
            var N = cin.ReadInt;
            var M = cin.ReadInt;
            var g = new Graph(N);
            for (int i = 0; i < M; ++i)
            {
                var a = cin.ReadInt - 1;
                var b = cin.ReadInt - 1;
                g.AddUnDirectedEdge(a, b);
            }

            var visited = new bool[N];
            var q = new Queue<State>();
            q.Enqueue(new State(0, 0));
            while (q.Any())
            {
                var now = q.Dequeue();
                visited[now.node] = true;
                if (now.node == N - 1 && now.dist <= 2) { WriteLine("POSSIBLE"); return; }
                if (now.dist >= 2) continue;
                foreach (var e in g[now.node])
                    if (!visited[e.To]) q.Enqueue(new State(e.To, now.dist + 1));
            }
            WriteLine("IMPOSSIBLE");
        }

        private struct State
        {
            public int node { get; set; }
            public int dist { get; set; }
            public State(int n, int d)
            {
                node = n;
                dist = d;
            }
        }
    }

    public class Graph
    {
        public struct Edge
        {
            public int To { get; set; }
            public long Cost { get; set; }
            public Edge(int to, long cost = 0, long cap = -1)
            {
                this.To = to;
                this.Cost = cost;
            }
        }

        private List<List<Edge>> g;
        public int N { get; private set; }
        public Graph(int size)
        {
            N = size;
            g = new List<List<Edge>>(size);
            for (int i = 0; i < size; i++) g.Add(new List<Edge>());
        }

        public List<Edge> this[int i]
        {
            get
            {
                if (i < 0 || i >= N) throw new IndexOutOfRangeException();
                return g[i];
            }
        }

        public void AddDirectedEdge(int from, int to, long cost = 0)
        {
            g[from].Add(new Edge(to, cost));
        }

        public void AddUnDirectedEdge(int from, int to, int cost = 0)
        {
            AddDirectedEdge(from, to, cost);
            AddDirectedEdge(to, from, cost);
        }
    }

    public class ConsoleInput
    {
        private readonly System.IO.TextReader _stream;
        private char _separator = ' ';
        private Queue<string> inputStream;
        public ConsoleInput(System.IO.TextReader stream, char separator = ' ')
        {
            this._separator = separator;
            this._stream = stream;
            inputStream = new Queue<string>();
        }
        public string Read
        {
            get
            {
                if (inputStream.Count != 0) return inputStream.Dequeue();
                string[] tmp = _stream.ReadLine().Split(_separator);
                for (int i = 0; i < tmp.Length; ++i)
                    inputStream.Enqueue(tmp[i]);
                return inputStream.Dequeue();
            }
        }
        public string ReadLine { get { return _stream.ReadLine(); }}
        public int ReadInt { get { return int.Parse(Read); }}
        public long ReadLong { get { return long.Parse(Read); }}
        public double ReadDouble { get { return double.Parse(Read); }}
        public string[] ReadStrArray(long N) { var ret = new string[N]; for (long i = 0; i < N; ++i) ret[i] = Read; return ret;}
        public int[] ReadIntArray(long N) { var ret = new int[N]; for (long i = 0; i < N; ++i) ret[i] = ReadInt; return ret;}
        public long[] ReadLongArray(long N) { var ret = new long[N]; for (long i = 0; i < N; ++i) ret[i] = ReadLong; return ret;}
        public void ReadIntArrays(long N, out int[] A, out int[] B) { A = new int[N]; B = new int[N]; for (long i = 0; i < N; ++i) { A[i] = ReadInt; B[i] = ReadInt; }}
        public void ReadLongArrays(long N, out long[] A, out long[] B) { A = new long[N]; B = new long[N]; for (long i = 0; i < N; ++i) { A[i] = ReadLong; B[i] = ReadLong; }}
    }
}

Measured memory_bytes: 49420