# input()

# int(input())

# map(int, input().split())

# list(map(int, input().split()))

# list(map(int, list(input()))) # スペースがない数字リストを読み込み

import math

import fractions

import sys

import bisect

import heapq  # 優先度付きキュー(最小値取り出し)

import collections

from collections import Counter

from collections import deque

import pprint



sr = lambda: eval(input())

ir = lambda: int(sr())

lr = lambda: list(map(int, sr().split()))



"""nを素因数分解"""

"""2以上の整数n => [[素因数, 指数], ...]の2次元リスト"""

def factorization(n):

    arr = []

    temp = n

    if n == 1:

        return arr



    for i in range(2, int(-(-n**0.5//1))+1):

        if temp%i==0:

            cnt=0

            while temp%i==0:

                cnt+=1

                temp //= i

            arr.append([i, cnt])



    if temp!=1:

        arr.append([temp, 1])



    if arr==[]:

        arr.append([n, 1])



    return arr



# a^n

def power(a,n,mod):

    x = 1

    while n:

        if n & 1:

            x *= a % mod

        n >>= 1

        a *= a % mod

    return x % mod



# n*(n-1)*...*(l+1)*l

def kaijo(n, l, mod):

    if n == 0:

        return 1

    a = n

    tmp = n-1

    while(tmp >= l):

        a = a*tmp%mod

        tmp -= 1

    return a



inf = 10**18

mod = 10**9+7



n = ir()

a = lr()

b = lr()



yoyu = []

muri = []



for i in range(n):

    if a[i] > b[i]:

        yoyu.append(a[i]-b[i])

    if a[i] < b[i]:

        muri.append(b[i]-a[i])



if sum(yoyu) < sum(muri):

    print((-1))

else:

    if muri:

        yoyu.sort(reverse=True)

        muri.sort()

        yoyu_ind = 0

        muri_ind = 0

        flag = False

        while muri_ind < len(muri):

            ret = muri[muri_ind]

            while ret > 0:

                if yoyu[yoyu_ind] > ret:

                    yoyu[yoyu_ind] -= ret

                    ret = 0

                    flag = False

                elif yoyu[yoyu_ind] == ret:

                    yoyu[yoyu_ind] -= ret

                    ret = 0

                    yoyu_ind+=1

                    flag = True

                else:

                    ret -= yoyu[yoyu_ind]

                    yoyu[yoyu_ind] = 0

                    yoyu_ind+=1

            muri_ind+=1

        if flag:

            print((muri_ind + yoyu_ind))

        else:

            print((muri_ind + yoyu_ind+1))

    else:

        print((0))
# input()

# int(input())

# map(int, input().split())

# list(map(int, input().split()))

# list(map(int, list(input()))) # スペースがない数字リストを読み込み

import math

import fractions

import sys

import bisect

import heapq  # 優先度付きキュー(最小値取り出し)

import collections

from collections import Counter

from collections import deque

import pprint

import itertools



sr = lambda: eval(input())

ir = lambda: int(sr())

lr = lambda: list(map(int, sr().split()))



"""nを素因数分解"""

"""2以上の整数n => [[素因数, 指数], ...]の2次元リスト"""





def factorization(n):

    arr = []

    temp = n

    if n == 1:

        return arr



    for i in range(2, int(-(-n ** 0.5 // 1)) + 1):

        if temp % i == 0:

            cnt = 0

            while temp % i == 0:

                cnt += 1

                temp //= i

            arr.append([i, cnt])



    if temp != 1:

        arr.append([temp, 1])



    if arr == []:

        arr.append([n, 1])



    return arr





# a^n

def power(a, n, mod):

    x = 1

    while n:

        if n & 1:

            x *= a % mod

        n >>= 1

        a *= a % mod

    return x % mod





# n*(n-1)*...*(l+1)*l

def kaijo(n, l, mod):

    if n == 0:

        return 1

    a = n

    tmp = n - 1

    while (tmp >= l):

        a = a * tmp % mod

        tmp -= 1

    return a



# Union Find

class UnionFind():

    def __init__(self, n):

        self.n = n

        self.parents = [-1] * n



    def find(self, x):

        if self.parents[x] < 0:

            return x

        else:

            self.parents[x] = self.find(self.parents[x])

            return self.parents[x]



    def union(self, x, y):

        x = self.find(x)

        y = self.find(y)



        if x == y:

            return



        if self.parents[x] > self.parents[y]:

            x, y = y, x



        self.parents[x] += self.parents[y]

        self.parents[y] = x



    def size(self, x):

        return -self.parents[self.find(x)]



    def same(self, x, y):

        return self.find(x) == self.find(y)



    def members(self, x):

        root = self.find(x)

        return [i for i in range(self.n) if self.find(i) == root]



    def roots(self):

        return [i for i, x in enumerate(self.parents) if x < 0]



    def group_count(self):

        return len(self.roots())



    def all_group_members(self):

        return {r: self.members(r) for r in self.roots()}



    def __str__(self):

        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())



# 約数生成

def make_divisors(n):

    divisors = []

    for i in range(1, int(n**0.5)+1):

        if n % i == 0:

            divisors.append(i)

            if i != n // i:

                divisors.append(n//i)



    divisors.sort()

    return divisors





inf = 10 ** 18

mod = 10 ** 9 + 7



n = ir()

a = lr()

b = lr()

if sum(b) > sum(a):

    print((-1))

else:

    p = []

    m = []

    for i in range(n):

        if a[i] > b[i]:

            p.append(a[i]-b[i])

        elif a[i] < b[i]:

            m.append(b[i]-a[i])

    p.sort(reverse=True)

    t = sum(m)

    ans = 0

    total = 0

    for num in p:

        if total < t:

            total+=num

            ans+=1

        else:

            break

    print((ans+len(m)))
# input()
# int(input())
# map(int, input().split())
# list(map(int, input().split()))
# list(map(int, list(input()))) # スペースがない数字リストを読み込み
import math
import fractions
import sys
import bisect
import heapq  # 優先度付きキュー(最小値取り出し)
import collections
from collections import Counter
from collections import deque
import pprint

sr = lambda: eval(input())
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))
"""nを素因数分解"""
"""2以上の整数n => [[素因数, 指数], ...]の2次元リスト"""


def factorization(n):
    arr = []
    temp = n
    if n == 1:
        return arr
    for i in range(2, int(-(-(n**0.5) // 1)) + 1):
        if temp % i == 0:
            cnt = 0
            while temp % i == 0:
                cnt += 1
                temp //= i
            arr.append([i, cnt])
    if temp != 1:
        arr.append([temp, 1])
    if arr == []:
        arr.append([n, 1])
    return arr


# a^n
def power(a, n, mod):
    x = 1
    while n:
        if n & 1:
            x *= a % mod
        n >>= 1
        a *= a % mod
    return x % mod


# n*(n-1)*...*(l+1)*l
def kaijo(n, l, mod):
    if n == 0:
        return 1
    a = n
    tmp = n - 1
    while tmp >= l:
        a = a * tmp % mod
        tmp -= 1
    return a


inf = 10**18
mod = 10**9 + 7
n = ir()
a = lr()
b = lr()
yoyu = []
muri = []
for i in range(n):
    if a[i] > b[i]:
        yoyu.append(a[i] - b[i])
    if a[i] < b[i]:
        muri.append(b[i] - a[i])
if sum(yoyu) < sum(muri):
    print((-1))
else:
    if muri:
        yoyu.sort(reverse=True)
        muri.sort()
        yoyu_ind = 0
        muri_ind = 0
        flag = False
        while muri_ind < len(muri):
            ret = muri[muri_ind]
            while ret > 0:
                if yoyu[yoyu_ind] > ret:
                    yoyu[yoyu_ind] -= ret
                    ret = 0
                    flag = False
                elif yoyu[yoyu_ind] == ret:
                    yoyu[yoyu_ind] -= ret
                    ret = 0
                    yoyu_ind += 1
                    flag = True
                else:
                    ret -= yoyu[yoyu_ind]
                    yoyu[yoyu_ind] = 0
                    yoyu_ind += 1
            muri_ind += 1
        if flag:
            print((muri_ind + yoyu_ind))
        else:
            print((muri_ind + yoyu_ind + 1))
    else:
        print((0))

# input()
# int(input())
# map(int, input().split())
# list(map(int, input().split()))
# list(map(int, list(input()))) # スペースがない数字リストを読み込み
import math
import fractions
import sys
import bisect
import heapq  # 優先度付きキュー(最小値取り出し)
import collections
from collections import Counter
from collections import deque
import pprint
import itertools

sr = lambda: eval(input())
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))
"""nを素因数分解"""
"""2以上の整数n => [[素因数, 指数], ...]の2次元リスト"""


def factorization(n):
    arr = []
    temp = n
    if n == 1:
        return arr
    for i in range(2, int(-(-(n**0.5) // 1)) + 1):
        if temp % i == 0:
            cnt = 0
            while temp % i == 0:
                cnt += 1
                temp //= i
            arr.append([i, cnt])
    if temp != 1:
        arr.append([temp, 1])
    if arr == []:
        arr.append([n, 1])
    return arr


# a^n
def power(a, n, mod):
    x = 1
    while n:
        if n & 1:
            x *= a % mod
        n >>= 1
        a *= a % mod
    return x % mod


# n*(n-1)*...*(l+1)*l
def kaijo(n, l, mod):
    if n == 0:
        return 1
    a = n
    tmp = n - 1
    while tmp >= l:
        a = a * tmp % mod
        tmp -= 1
    return a


# Union Find
class UnionFind:
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
        if x == y:
            return
        if self.parents[x] > self.parents[y]:
            x, y = y, x
        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return "\n".join("{}: {}".format(r, self.members(r)) for r in self.roots())


# 約数生成
def make_divisors(n):
    divisors = []
    for i in range(1, int(n**0.5) + 1):
        if n % i == 0:
            divisors.append(i)
            if i != n // i:
                divisors.append(n // i)
    divisors.sort()
    return divisors


inf = 10**18
mod = 10**9 + 7
n = ir()
a = lr()
b = lr()
if sum(b) > sum(a):
    print((-1))
else:
    p = []
    m = []
    for i in range(n):
        if a[i] > b[i]:
            p.append(a[i] - b[i])
        elif a[i] < b[i]:
            m.append(b[i] - a[i])
    p.sort(reverse=True)
    t = sum(m)
    ans = 0
    total = 0
    for num in p:
        if total < t:
            total += num
            ans += 1
        else:
            break
    print((ans + len(m)))

+import itertools +# Union Find +class UnionFind: +    def __init__(self, n): +        self.n = n +        self.parents = [-1] * n + +    def find(self, x): +        if self.parents[x] < 0: +            return x +        else: +            self.parents[x] = self.find(self.parents[x]) +            return self.parents[x] + +    def union(self, x, y): +        x = self.find(x) +        y = self.find(y) +        if x == y: +            return +        if self.parents[x] > self.parents[y]: +            x, y = y, x +        self.parents[x] += self.parents[y] +        self.parents[y] = x + +    def size(self, x): +        return -self.parents[self.find(x)] + +    def same(self, x, y): +        return self.find(x) == self.find(y) + +    def members(self, x): +        root = self.find(x) +        return [i for i in range(self.n) if self.find(i) == root] + +    def roots(self): +        return [i for i, x in enumerate(self.parents) if x < 0] + +    def group_count(self): +        return len(self.roots()) + +    def all_group_members(self): +        return {r: self.members(r) for r in self.roots()} + +    def __str__(self): +        return "\n".join("{}: {}".format(r, self.members(r)) for r in self.roots()) + + +# 約数生成 +def make_divisors(n): +    divisors = [] +    for i in range(1, int(n**0.5) + 1): +        if n % i == 0: +            divisors.append(i) +            if i != n // i: +                divisors.append(n // i) +    divisors.sort() +    return divisors + + -yoyu = [] -muri = [] -for i in range(n): -    if a[i] > b[i]: -        yoyu.append(a[i] - b[i]) -    if a[i] < b[i]: -        muri.append(b[i] - a[i]) -if sum(yoyu) < sum(muri): +if sum(b) > sum(a): -    if muri: -        yoyu.sort(reverse=True) -        muri.sort() -        yoyu_ind = 0 -        muri_ind = 0 -        flag = False -        while muri_ind < len(muri): -            ret = muri[muri_ind] -            while ret > 0: -                if yoyu[yoyu_ind] > ret: -                    yoyu[yoyu_ind] -= ret -                    ret = 0 -                    flag = False -                elif yoyu[yoyu_ind] == ret: -                    yoyu[yoyu_ind] -= ret -                    ret = 0 -                    yoyu_ind += 1 -                    flag = True -                else: -                    ret -= yoyu[yoyu_ind] -                    yoyu[yoyu_ind] = 0 -                    yoyu_ind += 1 -            muri_ind += 1 -        if flag: -            print((muri_ind + yoyu_ind)) +    p = [] +    m = [] +    for i in range(n): +        if a[i] > b[i]: +            p.append(a[i] - b[i]) +        elif a[i] < b[i]: +            m.append(b[i] - a[i]) +    p.sort(reverse=True) +    t = sum(m) +    ans = 0 +    total = 0 +    for num in p: +        if total < t: +            total += num +            ans += 1 -            print((muri_ind + yoyu_ind + 1)) -    else: -        print((0)) +            break +    print((ans + len(m)))