#include <bits/stdc++.h>
#define int long long
using namespace std;
pair<int,int> a[2005];
inline bool cmp(pair<int,int> a,pair<int,int> b)
{
	return a.first+a.second<b.first+b.second;
}
bitset <5000005> s;
//int dp[10][5000005];
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n,v,c;
	cin >> n >> v >> c;
	for(int i=1;i<=n;i++)
	{
		cin >> a[i].first >> a[i].second;
		a[i].second=(a[i].second*v-1)/c;
		a[i].second=min(a[i].second,4000000ll);
	}
	sort(a+1,a+n+1,cmp);
	s[0]=1;
//	dp[0][0]=1;
	for(int i=1;i<=n;i++)
	{
		s|=(s<<5000004-a[i].second)>>5000004-a[i].second-a[i].first;
/*		for(int j=0;j<=a[i].second;j++)
			dp[i][j+a[i].first]|=dp[i-1][j];
		for(int j=0;j<=5000000;j++)
			dp[i][j]|=dp[i-1][j];*/
	}
	int ans=0;
	for(int i=0;i<=5000000;i++)
		if(s[i]/*dp[n][i]*/) ans=max(ans,i*(c-1));
	for(int i=1;i<=n;i++) ans+=a[i].first;
	cout << ans;
	return 0;
}