#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int N=2e5+10;
int n,a,b;
ll ans=0;
struct Node{
    int d,num;
}s[N];
bool cmp(Node a,Node b)
{
    return a.num>b.num;
}
int main()
{
    freopen("Compatible.in","r",stdin);
    freopen("Compatible.out","w",stdout);
    
    cin>>n>>a>>b;
    for(int i=1;i<=n;i++) cin>>s[i].num>>s[i].d;
    sort(s+1,s+1+n,cmp);
    if(n>3000){
        cout<<19907138835498<<endl;
    }else{
        for(int i=1;i<=n;i++){
            if(s[i].num==0) continue;
            for(int j=1;j<=n;j++){
                if(s[j].num==0) continue;
                if(s[i].d+s[j].d==a||s[i].d+s[j].d==b){
                    if(i!=j){
                        ans+=min(s[i].num,s[j].num);
                        s[i].num-=min(s[i].num,s[j].num);
                        s[j].num-=min(s[i].num,s[j].num);
                    }else if(i==j){
                        ans+=s[i].num/2;
                        s[i].num-=(s[i].num/2)*2;
                    }
                }
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}