// C++ includes used for precompiling -*- C++ -*-
 
// Copyright (C) 2003-2013 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
 
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.
 
/** @file stdc++.h
 *  This is an implementation file for a precompiled header.
 */
 
// 17.4.1.2 Headers
 
// C
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
 
#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
//#include <cstdalign>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif
 
// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
 
#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif
 
using namespace std;
 
#define ms(s, n) memset(s, n, sizeof(s))
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define FORd(i, a, b) for (int i = (a) - 1; i >= (b); i--)
#define FORall(it, a) for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed<<setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcount(n)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<int> vi;
typedef vector<pi> vii;
typedef complex<double> base;
const int MOD = (int) 1e9 + 7;
const int INF = (int) 1e9;
const ll LINF = (ll) 1e18;
const ld PI = acos((ld) -1);
const ld EPS = 1e-9;
ll gcd(ll a, ll b) {ll r; while (b) {r = a % b; a = b; b = r;} return a;}
ll lcm(ll a, ll b) {return a / gcd(a, b) * b;}
ll fpow(ll n, ll k, int p = MOD) {ll r = 1;for (; k; k >>= 1) {if (k & 1) r = r * n % p; n = n * n % p;} return r;}
template<class T> void setmin(T& a, T val) {if (a > val) a = val;}
template<class T> void setmax(T& a, T val) {if (a < val) a = val;}
void addmod(ll& a, ll val, int p = MOD) {if ((a = (a + val)) >= p) a -= p;}
void submod(ll& a, ll val, int p = MOD) {if ((a = (a - val)) < 0) a += p;}
int mult(int a, int b, int p = MOD) {return (ll) a * b % p;}
ll inv(ll a, int p = MOD) {return fpow(a, p - 2, p);}
 

const int N=200005;
ll a[N],b[N];

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	
 	
 	 //For getting input from input.txt file
	//freopen("input.txt", "r", stdin);
 
	 //Printing the Output to output.txt file
	//freopen("output.txt", "w", stdout);

	int n;
	cin>>n;

	for(int i=1;i<=n;i++)
		cin>>a[i];
	

	for(int i=1;i<=n;i++)
		cin>>b[i];

	
	ll avsum=0,reqsum=0;
	for(int i=1;i<=n;i++)
	{
		if(a[i]>=b[i])
			avsum+=a[i]-b[i];
		else
			reqsum+=b[i]-a[i];
	}

	if(reqsum>avsum)
	{
		cout<<"-1\n";
		return 0;
	}


	vector<ll> v;
	
	for(int i=1;i<=n;i++)
	{
		if(a[i]>b[i])
			v.pb(a[i]-b[i]);
	}

	sort(v.begin(),v.end(),greater<int>());

	ll sum=0;int cnt=0;
	for(int i=0;i<v.size();i++)
	{
		if(sum<reqsum)
		{
			sum+=v[i];
			cnt++;
		}
		else 
			break;
	}

	for(int i=1;i<=n;i++)
	{
		if(a[i]<b[i])
			cnt++;
	}

	cout<<cnt<<"\n";

	return 0;
}

Measured memory_bytes: 2428