/*
Language: c++
Author: lxtgogogo
Date: 2016.04.15
*/
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<queue>
using namespace std;
inline int read(){
	int x=0;bool f=true;char ch=getchar();
	while(ch>'9' || ch<'0')	{if(ch=='-'){f=false;}ch=getchar();}
	while(ch>='0' && ch<='9')	{x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}
	return f?x:-x;
}
const int r=250010;
int n=0,ans=0;
int x[r]={},y[r]={};
bool f[r]={};
int used[r]={},len=0;

void init(){
	n=read();
	for(int i=1;i<=n;i++)	x[i]=read();
	for(int i=1;i<=n;i++)	y[i]=read();
}
void dfs(int i,long long sum,int num){
	if(i==n+1)
	{
		if(num>ans)	ans=num;
		return ;
	}
	if(num+n-i+1<ans)	return ;
	sum+=x[i];
	if(sum>=y[i])	dfs(i+1,sum-y[i],num+1);
	dfs(i+1,sum,num);
}
void work1(){
	long long sum=0;
	for(int i=1;i<=n;i++)
	{
		sum+=x[i];
		if(sum>=y[i])	{f[i]=true;sum-=y[i];ans++;}
		else
		{
			int maxx=i;
			for(int j=1;j<i;j++)
				if(f[j] && y[j]>y[maxx])
					maxx=j;
			if(maxx!=i)
			{
				f[maxx]=false;f[i]=true;
				sum+=y[maxx];sum-=y[i];
			}
		}
	}
	printf("%d\n",ans);
}
void work2(){
	long long sum=0;
	for(int i=1;i<=n;i++)
	{
		sum+=x[i];
		if(sum>=y[i])
		{
			int j=len;
			while(y[used[j]]>y[i] && j>1)	j--;//维护一个单调增数组，往里插入
			for(int k=len;k>=j;k--)	used[k+1]=used[k];
			used[j]=i;len++;
			f[i]=true;
			sum-=y[i];
			ans++;
		}
		else if(y[i]<used[len])
		{
			f[used[len]]=false;f[i]=true;
			sum+=y[used[len]];sum-=y[i];
			int j=len-1;
			while(y[used[j]]>y[i] && j>1)	j--;
			for(int k=len-1;k>=j;k--)	used[k+1]=used[k];
			used[j]=i;
		}
	}
	printf("%d\n",ans);
}
int main(){
	freopen("wing.in","r",stdin);
	freopen("wing.out","w",stdout);
	
	init();
	if(n<=20)	{dfs(1,0,0);printf("%d\n",ans);}
	if(n<=1000)	work1();
	else work2();
	
	fclose(stdin);fclose(stdout);
	return 0;
}