代码：

#include <iostream>
#include <algorithm>
using namespace std;

struct st
{
	int x, y;
};
bool cmp(st a, st b)
{
	return a.y < b.y;
}
st c[5001];
int main()
{
	int n, s, cnt = 0;
	cin >> n >> s;
	int a, b;
	cin >> a >> b;
	for (int i = 1; i <= n; ++i)
	{
		cin >> c[i].x >> c[i].y;
	}
	sort(c + 1, c + n + 1, cmp);
	for (int i = 1; i <= n; ++i)
	{
		if (s - c[i].y < 0 || a + b < c[i].x)
		{
			break;
		}
		cnt++;
		s -= c[i].y;
	}
	cout << cnt << endl;
	return 0;
}