#include<bits/stdc++.h>
#pragma optimize GCC(2)
using namespace std;
struct shorter
{
	int height,arm,sum;
}p[10000];
bool cmp(shorter a,shorter b)
{
	return a.sum <b.sum ;
}
int main()
{
	int n;
	cin>>n;
	int s=0;
	for(int i=1;i<=n;i++)
	{
		cin>>p[i].height >>p[i].arm ;
		p[i].sum =p[i].arm +p[i].height ;
		s+=p[i].sum ;
	}
	int high,ans=0;
	cin>>high;
	sort(p+1,p+n+1,cmp);
	for(int i=1;i<=n;i++)
	{
		if(s<high)
		{
			break;
		}
		else
		{
			s-=p[i].sum ;ans++;
		}
	}
	cout<<ans;
	
		return 0;
}

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