using System;
using System.Text;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using E = System.Linq.Enumerable;
using System.IO.Pipes;

class Program
{
    static char[] abc = "abcdefghijklmnopqrstuvwxyz".ToCharArray();
    static long mod = 1000000007;
    static void Main(string[] args)
    {
        //var S = Console.ReadLine();
        //var A = long.Parse(Console.ReadLine());
        var N = long.Parse(Console.ReadLine());
       var A = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
        var B = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
        long ans = 0;
        long sum = 0;
        var pq = new PriorityQueue<long>();
        var plus = 0;
        var pp = new long[N];
        for (int i = 0; i < N; i++)
        {
            var C = A[i] - B[i];
            if(C < 0)

            {
                ans++;
                sum += C;
            }
            else if(C > 0)
            {
                pp[plus] = C;
                plus++;
            }
        }

        Array.Sort(pp);
        Array.Reverse(pp);
        var now = 0;
        while (plus > 0 && sum < 0)
        {
            ans++;
            plus--;
            var top = pp[now];
            now++;
            sum += top;
        }

        Console.WriteLine(sum >= 0 ?ans:-1);
        
    }



}


public class PriorityQueue<T> : IEnumerable<T>
{
    private readonly List<T> _data = new List<T>();
    private readonly IComparer<T> _comparer;
    private readonly bool _isDescending;

    public PriorityQueue(IComparer<T> comparer, bool isDescending = true)
    {
        _comparer = comparer;
        _isDescending = isDescending;
    }

    public PriorityQueue(Comparison<T> comparison, bool isDescending = true)
        : this(Comparer<T>.Create(comparison), isDescending)
    {
    }

    public PriorityQueue(bool isDescending = true)
        : this(Comparer<T>.Default, isDescending)
    {
    }

    public void Enqueue(T item)
    {
        _data.Add(item);
        var childIndex = _data.Count - 1;
        while (childIndex > 0)
        {
            var parentIndex = (childIndex - 1) / 2;
            if (Compare(_data[childIndex], _data[parentIndex]) >= 0)
                break;
            Swap(childIndex, parentIndex);
            childIndex = parentIndex;
        }
    }

    public T Dequeue()
    {
        var lastIndex = _data.Count - 1;
        var firstItem = _data[0];
        _data[0] = _data[lastIndex];
        _data.RemoveAt(lastIndex--);
        var parentIndex = 0;
        while (true)
        {
            var childIndex = parentIndex * 2 + 1;
            if (childIndex > lastIndex)
                break;
            var rightChild = childIndex + 1;
            if (rightChild <= lastIndex && Compare(_data[rightChild], _data[childIndex]) < 0)
                childIndex = rightChild;
            if (Compare(_data[parentIndex], _data[childIndex]) <= 0)
                break;
            Swap(parentIndex, childIndex);
            parentIndex = childIndex;
        }
        return firstItem;
    }

    public T Peek()
    {
        return _data[0];
    }

    private void Swap(int a, int b)
    {
        var tmp = _data[a];
        _data[a] = _data[b];
        _data[b] = tmp;
    }

    private int Compare(T a, T b)
    {
        return _isDescending ? _comparer.Compare(b, a) : _comparer.Compare(a, b);
    }

    public int Count => _data.Count;

    public IEnumerator<T> GetEnumerator()
    {
        return _data.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}

Measured memory_bytes: 43720