include [HTML_REMOVED]
include [HTML_REMOVED]
using namespace std;
int n, w, a, b,res;
struct guaishou
{
int x;
int y;
} t[5050];
bool cmp(guaishou m, guaishou n)
{
return m.y < n.y;
}
int main()
{
cin >> n >> w >> a >> b;
int k = a + b;
for (int i = 1; i <= n; i)
{
cin >> t[i].x >> t[i].y;
}
sort(t + 1, t + 1 + n, cmp);
for (int i = 1; i <= n; i)
{
if (w-t[i].y >= 0 && k >= t[i].x)
{
res++;
w -= t[i].y;
}
if(w<0)break;
else
continue;
}
cout << res;
return 0;
}