import java.io.*;
import java.util.*;

class Main {
    public static void main(String args[]) throws IOException {
        Scan sc= new Scan();
        int n = sc.scanInt();
        int m = sc.scanInt();
        List<Integer>[] adjList = new ArrayList[n+1];
        for(int i = 1;i <= n; ++i){
            adjList[i] = new ArrayList<Integer>();
        }
        while(m-- > 0){
            int a = sc.scanInt();
            int b = sc.scanInt();
            adjList[a].add(b);
            adjList[b].add(a);
        }
        
        Queue<Node> q = new LinkedList<>();
        q.add(new Node(1,0));
        int[] vis = new int[n+1];
        vis[1] = 1;
        while(!q.isEmpty()){
            Node curr = q.poll();
            for(int nbr : adjList[curr.val]){
                if(nbr == curr.val)
                    continue;
                if(nbr == n){
                    System.out.println(curr.dep == 1 ? "POSSIBLE" : "IMPOSSIBLE");
                    return;
                }
                if(vis[nbr] == 0){
                    vis[nbr] = 1;
                    q.offer(new Node(nbr, curr.dep+1));
                }
            }
        }
        System.out.println("IMPOSSIBLE");
    }
}

class Node {
    int val, dep;
    Node(int val, int dep){
        this.val = val;
        this.dep = dep;
    }
}
class Scan
{
    private byte[] buf=new byte[1024];
    private int index;
    private InputStream in;
    private int total;
    public Scan()
    {
        in=System.in;
    }
    public int scan()throws IOException
    {
        if(total<0)
        throw new InputMismatchException();
        if(index>=total)
        {
            index=0;
            total=in.read(buf);
            if(total<=0)
            return -1;
        }
        return buf[index++];
    }
    public int scanInt()throws IOException
    {
        int integer=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n))
        {
            if(n>='0'&&n<='9')
            {
                integer*=10;
                integer+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        return neg*integer;
    }
    public long scanLong() throws IOException {
        long integer=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n))
        {
            if(n>='0'&&n<='9')
            {
                integer*=10;
                integer+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        return neg*integer;
    }
    public double scanDouble()throws IOException
    {
        double doub=0;
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        int neg=1;
        if(n=='-')
        {
            neg=-1;
            n=scan();
        }
        while(!isWhiteSpace(n)&&n!='.')
        {
            if(n>='0'&&n<='9')
            {
                doub*=10;
                doub+=n-'0';
                n=scan();
            }
            else throw new InputMismatchException();
        }
        if(n=='.')
        {
            n=scan();
            double temp=1;
            while(!isWhiteSpace(n))
            {
                if(n>='0'&&n<='9')
                {
                    temp/=10;
                    doub+=(n-'0')*temp;
                    n=scan();
                }
                else throw new InputMismatchException();
            }
        }
        return doub*neg;
    }
    public String scanString()throws IOException
    {
        StringBuilder sb=new StringBuilder();
        int n=scan();
        while(isWhiteSpace(n))
        n=scan();
        while(!isWhiteSpace(n))
        {
            sb.append((char)n);
            n=scan();
        }
        return sb.toString();
    }
    private boolean isWhiteSpace(int n)
    {
        if(n==' '||n=='\n'||n=='\r'||n=='\t'||n==-1)
        return true;
        return false;
    }
}


Measured memory_bytes: 69476