#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll,ll> 
#define fi first
#define se second
vector<ll> v;
map<ll,ll> id;
bool cmp(pii x,pii y){return x.se<y.se;}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	ll n,A,B;cin>>n>>A>>B;
	for(ll i=1,d,x;i<=n;i++){
		cin>>x>>d;
		id[d]=x;
		v.push_back(d);
	}
	sort(v.begin(),v.end());
    ll ans=0;
	for(auto x:v){
		ll pa=A-x,pb=B-x;
		if(id[pb]>0&&pb>=0){//应该优先匹配pb 
			if(pb==x) ans+=id[pb]/2,id[pb]%=2;
			else{
				int mi=min(id[x],id[pb]);
				ans+=mi;
				id[x]-=mi,id[pb]-=mi;
			}
		} 
		if(id[pa]>0&&pa>=0){
			if(pa==x) ans+=id[pa]/2,id[pa]%=2;
			else {
				int mi=min(id[x],id[pa]);
				ans+=mi;
				id[x]-=mi,id[pa]-=mi; 
			}
		}
	}
	cout<<ans;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<ll,ll> 
#define fi first
#define se second
vector<ll> v;
map<ll,ll> id;
bool cmp(pii x,pii y){return x.se<y.se;}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	ll n,A,B;cin>>n>>A>>B;
	for(ll i=1,d,x;i<=n;i++){
		cin>>x>>d;
		id[d]=x;
		v.push_back(d);
	}
	sort(v.begin(),v.end());
    ll ans=0;
	for(auto x:v){
		ll pa=A-x,pb=B-x;
		if(id[pb]>0&&pb>=0){//应该优先匹配pb 
			if(pb==x) ans+=id[pb]/2,id[pb]%=2;
			else{
				int mi=min(id[x],id[pb]);
				ans+=mi;
				id[x]-=mi,id[pb]-=mi;
			}
		} 
		if(id[pa]>0&&pa>=0){
			if(pa==x) ans+=id[pa]/2,id[pa]%=2;
			else {
				int mi=min(id[x],id[pa]);
				ans+=mi;
				id[x]-=mi,id[pa]-=mi; 
			}
		}
	}
	cout<<ans;
	return 0;
}