using System;

namespace No110{
    public class Program{
        public static void Main(string[] args){
            var sr = new StreamReader();
            //---------------------------------
            var n = new int[2];
            var block = new int[2][];
            for(var i = 0; i < 2; i++){
                n[i] = sr.Next<int>();
                block[i] = sr.Next<int>(n[i]);
                Array.Sort(block[i]);
            }

            var max = 0;
            for(var i = 0; i < 2; i++){
                var cColor = i;
                var cSize = 0;
                var height = 0;
                while(true){
                    var next = Array.BinarySearch(block[cColor], cSize + 1);
                    if(next <= -1)  next = ~next;
                    if(next == block[cColor].Length) break;
                    cSize = block[cColor][next];
                    cColor ^= 1;
                    height++;
                }
                max = Math.Max(max, height);
            }

            Console.WriteLine(max);
            //---------------------------------
        }
    }

    public class StreamReader{
        private readonly char[] _c = {' '};
        private int _index = -1;
        private string[] _input = new string[0];

        public T Next<T>(){
            if(_index == _input.Length - 1){
                _index = -1;
                while(true){
                    string rl = Console.ReadLine();
                    if(rl == null){
                        if(typeof(T).IsClass) return default(T);
                        return (T)typeof(T).GetField("MinValue").GetValue(null);
                    }
                    if(rl != ""){
                        _input = rl.Split(_c, StringSplitOptions.RemoveEmptyEntries);
                        break;
                    }
                }
            }
            return (T)Convert.ChangeType(_input[++_index], typeof(T), System.Globalization.CultureInfo.InvariantCulture);
        }

        public T[] Next<T>(int x){
            var ret = new T[x];
            for(var i = 0; i < x; ++i) ret[i] = Next<T>();
            return ret;
        }
    }
}