#include<bits/stdc++.h>
using namespace std;
const int N=2510;
int f[N][N],p,q;
int n,a[N],b[N];
int main()
{
freopen("food.in","r",stdin);
freopen("food.out","w",stdout);
scanf("%d%d%d",&n,&p,&q);
for (int i=1;i<=n;i++) scanf("%d%d",&a[i],&b[i]);
f[0][0]=1;
for (int i=1;i<=n;i++)
{
for (int j=p;j>=a[i];j--)
for (int k=q;k>=b[i];k--)
f[j][k]+=f[j-a[i]][k-b[i]];
}
printf("%d",f[p][q]);
return 0;
}