#include <bits/stdc++.h>
using namespace std;
#define ll long long

map<ll,ll> mp;
vector<ll> vs;
ll n,a,b,ans;

int main(){
//	freopen("in.in","r",stdin);
	freopen("Compatible.in","r",stdin);
	freopen("Compatible.out","w",stdout);
	scanf("%lld %lld %lld",&n,&a,&b);
	for(ll i=1;i<=n;i++){
		ll u,v;
		scanf("%lld %lld",&u,&v);
		mp[v]=u;
		vs.push_back(v);
	}
	sort(vs.begin(),vs.end());
	for(ll i=0;i<n;i++){
		ll x=vs[i];
		ll pa=a-x,pb=b-x;
		if(mp[pb]>0 && pb>=0){
			if(pb==x) ans+=mp[pb]/2,mp[pb]%=2;
			else{
				ll minn=min(mp[x],mp[pb]);
				ans+=minn;
				mp[x]-=minn;
				mp[pb]-=minn;
			}
		}
		if(mp[pa]>0&&pa>=0){
			if(pa==x) ans+=mp[pa]/2,mp[pa]%=2;
			else{
				ll minn=min(mp[x],mp[pa]);
				ans+=minn;
				mp[x]-=minn;
				mp[pa]-=minn;
			}
		}
	}
	printf("%lld",ans);
	return 0;
}