import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
 
public class Main {
    FastScanner in = new FastScanner(System.in);
    PrintWriter out = new PrintWriter(System.out);
 
    public static void main(String[] args) {
        new Main().calc();
    }
    
    public void calc() {
        int N = in.nextInt(), M = in.nextInt();
        int[] a = new int[M];
        int[] b = new int[M];
 
        // 定期便の組み合わせが入るMap。
        // key: 定期便の出発元の島, value: keyの島から定期便が出ている出発先の島のList
        Map<Integer, List<Integer>> map = new HashMap<Integer, List<Integer>>();
        
        for (int i = 0; i < M; i++) {
            a[i] = in.nextInt() - 1;
            b[i] = in.nextInt() - 1;
            // mapにa[i], b[i]を追加
            List<Integer> list = map.getOrDefault(a[i], new ArrayList<Integer>());
            list.add(b[i]);
            map.put(a[i], list);
        }
        
        // 島0から定期便で行ける先のList
        List<Integer> viaList = map.get(0);
        String ans = "IMPOSSIBLE";
        
        // 島0から行ける島を経由地とし，各経由地について
        outside: for (Integer via : viaList) {
            // 経由地から行ける島のListを取得
            for (Integer dest: map.getOrDefault(via, new ArrayList<Integer>())) {
                // 経由地から島N(0オリジンなのでN-1)に行ければ答えはPOSSIBLE
                if (dest == N - 1) {
                    ans = "POSSIBLE";
                    break outside;
                }
            }
        }
        
        out.println(ans);
        out.close();
    }
    
    class FastScanner {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
 
        public FastScanner(InputStream stream) {
            this.stream = stream;
        }
 
        int read() {
            if (numChars == -1)
                throw new InputMismatchException();
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
 
        boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
 
        boolean isEndline(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }
 
        int nextInt() {
            return Integer.parseInt(next());
        }
 
        int[] nextIntArray(int n) {
            int[] array = new int[n];
            for (int i = 0; i < n; i++)
                array[i] = nextInt();
 
            return array;
        }
 
        int[][] nextIntMap(int n, int m) {
            int[][] map = new int[n][m];
            for (int i = 0; i < n; i++) {
                map[i] = in.nextIntArray(m);
            }
            return map;
        }
 
        long nextLong() {
            return Long.parseLong(next());
        }
 
        long[] nextLongArray(int n) {
            long[] array = new long[n];
            for (int i = 0; i < n; i++)
                array[i] = nextLong();
 
            return array;
        }
 
        long[][] nextLongMap(int n, int m) {
            long[][] map = new long[n][m];
            for (int i = 0; i < n; i++) {
                map[i] = in.nextLongArray(m);
            }
            return map;
        }
 
        double nextDouble() {
            return Double.parseDouble(next());
        }
 
        double[] nextDoubleArray(int n) {
            double[] array = new double[n];
            for (int i = 0; i < n; i++)
                array[i] = nextDouble();
 
            return array;
        }
 
        double[][] nextDoubleMap(int n, int m) {
            double[][] map = new double[n][m];
            for (int i = 0; i < n; i++) {
                map[i] = in.nextDoubleArray(m);
            }
            return map;
        }
 
        String next() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }
 
        String[] nextStringArray(int n) {
            String[] array = new String[n];
            for (int i = 0; i < n; i++)
                array[i] = next();
 
            return array;
        }
 
        String nextLine() {
            int c = read();
            while (isEndline(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndline(c));
            return res.toString();
        }
    }
}

Measured memory_bytes: 77964