2 3
1 2 1 3
1 2 1 3 2 3
 3 7
8 2 7 9 8 1
3 1 8 1 2 7 4 7 4 2 1 4 4 6
 1 10
3 9
3 2 3 4 5 3 5 7 8 6 2 5 7 8 2 4 1 7 5 1
 12 1
6 2 6 4 8 6 6 9 5 6 6 1 9 1 1 3 3 9 2 4 5 2 8 1
6 7
 2 3
1 2 7 8
1 3 2 4 7 9
 3 2
1 2 1 3 2 3
1 2 4 5
 3 8
8 9 8 5 9 2
8 4 8 3 2 6 4 2 4 3 3 7 3 6 1 6
 8 5
7 9 6 7 4 7 2 1 4 9 2 9 4 2 9 6
8 7 1 8 8 5 3 5 3 8
 4 4
1 2 1 3 6 7 6 8
1 4 1 5 6 1 6 9
 3 10
6 1 4 1 4 6
7 1 8 1 8 5 3 2 9 7 9 3 5 9 5 3 5 7 7 2
 3 3
1 2 1 3 2 3
1 2 1 3 2 3
 11 1
2 6 1 4 7 9 7 6 8 1 4 8 4 7 7 2 1 7 9 6 6 5
3 1
 5 6
1 7 5 6 6 9 3 6 1 9
2 7 2 5 8 5 4 8 4 2 8 2
 8 1
1 6 7 6 7 3 9 2 1 2 8 6 2 3 4 1
8 3
 9 4
2 8 8 9 8 1 9 2 5 9 3 5 3 2 5 2 9 1
8 4 8 7 6 8 4 7
 4 7
9 2 4 1 2 3 2 7
6 1 5 4 7 5 6 3 1 5 8 1 1 4
 3 3
1 2 5 6 7 8
2 3 4 5 8 9
 1 7
8 4
9 8 8 2 6 8 8 1 7 8 2 1 9 5
 2 2
1 2 2 3
2 3 3 4
 12 12
6 7 5 4 7 8 2 9 8 5 3 5 1 6 7 3 7 9 5 7 1 8 6 8
6 4 2 1 7 8 1 6 8 5 9 8 1 5 7 2 5 9 6 3 9 2 9 4
 9 1
3 4 3 2 3 7 3 5 9 4 1 9 6 4 5 2 7 6
8 3
 9 2
9 6 1 6 2 5 7 3 8 1 7 2 9 1 2 8 3 8
6 4 4 5
 3 9
9 7 9 2 7 2
9 8 1 9 3 9 6 3 8 6 4 6 1 3 5 4 5 3
 3 6
3 5 7 4 7 5
3 9 3 2 8 6 6 2 8 2 6 9
 2 1
1 2 1 3
1 2
 9 1
1 8 7 6 7 2 7 9 4 1 4 3 3 8 4 6 9 6
9 4
 2 2
1 2 2 4
1 2 1 3
 6 9
8 1 8 4 2 8 2 1 4 1 4 2
8 3 8 6 7 8 5 8 6 7 5 7 9 6 5 6 5 3
 12 2
3 1 8 2 6 9 2 6 5 4 4 3 4 1 4 2 6 3 9 7 9 4 3 2
7 1 4 1
 2 1
4 5 6 7
4 7
 4 3
1 2 4 5 6 7 8 9
1 2 8 9 3 1
 12 12
7 6 3 8 8 4 4 7 1 9 9 5 7 5 4 9 8 6 2 7 7 3 3 6
9 1 2 4 9 8 5 3 6 7 3 8 2 7 5 9 6 4 3 1 2 6 1 4
 12 5
9 2 6 7 7 8 3 4 8 4 7 1 2 1 7 3 7 2 5 6 3 8 1 5
3 7 7 5 7 4 5 8 4 6
 7 6
6 2 9 2 6 5 2 4 1 2 4 5 6 7
3 9 5 1 9 8 9 5 3 4 2 3
 6 4
2 7 3 2 8 3 1 5 7 4 3 5
2 6 9 8 8 6 6 9
 10 2
4 9 2 1 5 1 6 2 6 7 2 7 5 8 1 7 5 3 9 1
9 7 1 4
 4 4
1 2 2 3 1 3 4 5
1 3 3 2 1 2 4 6
 3 4
2 1 8 9 3 1
1 2 4 5 6 7 8 9
 1 12
6 8
8 4 8 2 5 8 9 8 8 3 8 7 8 1 1 3 1 9 4 3 7 3 5 7
 4 4
1 2 3 4 5 6 7 8
2 3 4 5 6 7 8 1
 3 10
1 5 7 1 2 1
9 5 5 6 3 5 4 7 8 3 9 6 8 4 9 8 4 6 3 4
 3 2
1 2 4 5 6 7
4 7 1 3
 5 6
4 7 7 3 4 3 9 4 3 9
7 5 7 8 1 7 7 2 6 2 1 2
 7 3
2 6 6 7 6 4 6 1 9 6 7 4 1 9
6 5 3 6 6 8
 2 7
2 7 2 5
7 1 9 7 8 9 4 9 8 1 3 9 3 8
 2 2
1 2 1 3
1 2 1 3
 2 11
6 1 3 6
1 7 1 2 1 5 1 4 5 3 3 2 9 8 4 2 7 5 4 9 2 9
 12 12
1 6 2 6 8 3 6 4 4 8 7 2 7 5 9 4 2 4 9 5 8 5 3 6
2 8 6 9 2 6 7 4 6 5 6 3 5 8 7 8 7 1 1 9 9 7 7 3
 4 12
2 8 3 1 2 1 9 4
9 5 5 3 1 6 3 7 7 1 8 5 6 5 4 6 1 9 1 4 2 5 9 8

-1 -1 3 6 -1 -1 0 0 -1 1 -1 1 0 -1 8 -1 0 8 0 -1 3 0 9 3 1 -1 0 8 -1 -1 1 -1 -1 -1 0 -1 -1 1 8 -1 0 -1 7 6 7 1 0 -1 -1
import java.io.*;
import java.util.*;

/*
TASK: CFB
LANG: JAVA
 */
public class CFB {
    static int n , m;
    static int[][] a , b;
    static boolean[] share = new boolean[10];
    public static void main(String[] args) throws IOException {
        FastScanner in = new FastScanner(System.in);
        n = in.nextInt();
        m = in.nextInt();
        a = new int[n][2];
        b = new int[m][2];
        for(int i= 0;i < n; i++){
            a[i][0] = in.nextInt();
            a[i][1] = in.nextInt();
            Arrays.sort(a[i]);
        }
        for(int j = 0;j < m; j++){
            b[j][0] = in.nextInt();
            b[j][1] = in.nextInt();
            Arrays.sort(b[j]);
        }
        for(int i = 0;i < n; i++){
            int[] cnt = new int[2];
            for(int j = 0;j < m; j++){
                if(a[i][0] == b[j][0] && a[i][1] == b[j][1])continue;
                for(int k= 0;k < 2; k++){
                    for(int l = 0;l < 2; l++){
                        if(b[j][k] == a[i][l])cnt[l]++;
                    }
                }
            }
            if(cnt[0] > 0 && cnt[1] > 0){
                System.out.println(-1);
                return;
            }
            if(cnt[0] > 0)share[a[i][0]] = true;
            if(cnt[1] > 0)share[a[i][1]] = true;
        }
        for(int i = 0;i < m; i++){
            int[] cnt = new int[2];
            for(int j = 0;j < n; j++){
                if(b[i][0] == a[j][0] && b[i][1] == a[j][1])continue;
                for(int k= 0;k < 2; k++){
                    for(int l = 0;l < 2; l++){
                        if(a[j][k] == b[i][l])cnt[l]++;
                    }
                }
            }
            if(cnt[0] > 0 && cnt[1] > 0){
                System.out.println(-1);
                return;
            }
            if(cnt[0] > 0)share[b[i][0]] = true;
            if(cnt[1] > 0)share[b[i][1]] = true;
        }
        int c = 0;
        for(int i = 1;i <= 9; i++){
            if(share[i])c++;
        }
        if(c > 1)System.out.println(0);
        else System.out.println(1);
    }

    static class FastScanner {
        final private int BUFFER_SIZE = 1 << 20;
        private DataInputStream din;
        private byte[] buffer;
        private int bufferPointer, bytesRead;

        public FastScanner(InputStream stream) {
            din = new DataInputStream(stream);
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        public FastScanner(String file_name) throws IOException {
            din = new DataInputStream(new FileInputStream(file_name));
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        int[] nextIntArray(int N) throws IOException {
            int[] arr = new int[N];
            for (int i = 0; i < N; i++) {
                arr[i] = nextInt();
            }
            return arr;
        }

        String nextLine() throws IOException {
            int c = read();
            while (c != -1 && isEndline(c))
                c = read();
            if (c == -1) {
                return null;
            }
            StringBuilder res = new StringBuilder();
            do {
                if (c >= 0) {
                    res.appendCodePoint(c);
                }
                c = read();
            } while (!isEndline(c));
            return res.toString();
        }

        public String nextLine(int maxLen) throws IOException {
            byte[] buf = new byte[maxLen]; // line length
            int cnt = 0, c;
            while ((c = read()) != -1) {
                if (c == '\n') break;
                buf[cnt++] = (byte) c;
            }
            return new String(buf, 0, cnt);
        }

        boolean isEndline(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }

        String next() throws Exception {
            int c = readOutSpaces();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public int nextInt() throws IOException {
            int ret = 0;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg) c = read();
            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');

            if (neg) return -ret;
            return ret;
        }

        public long nextLong() throws IOException {
            long ret = 0;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg) c = read();
            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');
            if (neg) return -ret;
            return ret;
        }

        public double nextDouble() throws IOException {
            double ret = 0, div = 1;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg) c = read();

            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');

            if (c == '.') {
                while ((c = read()) >= '0' && c <= '9') {
                    ret += (c - '0') / (div *= 10);
                }
            }

            if (neg) return -ret;
            return ret;
        }

        private void fillBuffer() throws IOException {
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
            if (bytesRead == -1) buffer[0] = -1;
        }

        private byte read() throws IOException {
            if (bufferPointer == bytesRead) fillBuffer();
            return buffer[bufferPointer++];
        }

        private int readOutSpaces() throws IOException {
            while (true) {
                if (bufferPointer == bytesRead) fillBuffer();
                int c = buffer[bufferPointer++];
                if (!isSpaceChar(c)) {
                    return c;
                }
            }
        }

        public void close() throws IOException {
            if (din == null) return;
            din.close();
        }
    }
}
