using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Practice
{
    class Program
    {
        static void Main(string[] args)
        {
            Solve();
        }
        private const int MOD = 1000000007;
        private const string Keyence = "keyence";
        private struct AB
        {
            public long a;
            public long b;
            public AB(long a, long b)
            {
                this.a = a;
                this.b = b;
            }
        }

        static void Solve()
        {
            int n = ReadAndParseInt();
            var a = ReadAndParseLongArr();
            var b = ReadAndParseLongArr();
            var ab = new List<AB>(n);
            for(int i=0;i<n;++i)
            {
                ab.Add( new AB(a[i], b[i]));
            }

            ab.Sort((i, j) => i.b.CompareTo(j.b));
            var c = new long[n];
            long totalA = a.Sum();
            for(int i=0;i<n;++i)
            {
                c[i] = ab[i].b;
                totalA -= c[i];
                if( totalA < 0)
                {
                    Console.WriteLine(-1);
                    return;
                }
            }
            // 残ったポイントをA C が同一になるように振り分けるぞ
            var d = new long[n];
            for(int i=0;i<n;++i)
            {
                d[i] = ab[i].a - c[i];
            }

            var listD = new List<long>(d);
            listD.Sort();
            // totalA を振り分け　0にしたい、負の値はどうしよもないが
            for(int i=0;i<n;++i)
            {
                if( listD[i] <= 0) { continue; }
                if( listD[i] <= totalA)
                {
                    totalA -= listD[i];
                    listD[i] = 0;
                }else
                {
                    totalA = 0;
                    listD[i] -= totalA;
                }
            }
            // 異なる値は？
            long ans = 0;
            for(int i=0;i<n;++i)
            {
                if( listD[i] != 0)
                { ans++; }
            }
            Console.WriteLine(ans);
        }
        private static bool IsValidFront (string sz)
        {
            return sz.StartsWith(Keyence);
        }
        private static bool IsValidBack(string sz)
        {
            return sz.EndsWith(Keyence);
        }
        #region よく使う便利関数
        private static bool isPrime(long x)
        {
            if (x == 2) { return true; }
            if (x < 2 || x % 2 == 0) { return false; }
            long i = 3;
            while (i * i <= x)
            {
                if (x % i == 0) { return false; }
                i = i + 2;
            }
            return true;
        }
        private static long lcm(long x, long y)
        {
            return x / gcd(x, y) * y;
        }
        private static long gcd(long x, long y)
        {
            return y > 0 ? gcd(y, x % y) : x;
        }
        private static long pow(long x, long n)
        {
            if (n == 0) { return 1; }
            long res = pow(x * x % MOD, n / 2);
            if (n % 2 == 1)
            {
                res = res * x % MOD;
            }
            return res;
        }
        private static int ReadAndParseInt()
        {
            return int.Parse(Console.ReadLine());
        }
        private static int[] ReadAndParseIntArr()
        {
            return Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
        }
        private static long ReadAndParseLong()
        {
            return long.Parse(Console.ReadLine());
        }
        private static long[] ReadAndParseLongArr()
        {
            return Array.ConvertAll(Console.ReadLine().Split(' '), long.Parse);
        }
        #endregion
    }
}

Measured memory_bytes: 38000