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#include <bits/stdc++.h>
#include <unistd.h>
using namespace std;
typedef long long ll;
typedef double db;
typedef long double ldb;
const ll MAXN=5e4+5;
ll n,a[MAXN],b[MAXN],ans,index=1;
int main() {
	cin>>n;
	for(ll i=1;i<=n;++i){
		cin>>a[i];
	}
	for(ll i=1;i<=n;++i){
		cin>>b[i];
	}
	sort(a+1,a+n+1);
	sort(b+1,b+n+1);
	for(ll i=1;i<=n;++i){
		if(a[i]>=b[index]){
			++ans;
			++index;
		}
	}
	cout<<ans<<endl;
	return 0;
}