#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=2e5+10;
#define PII pair<int,int>
#define fi first
#define se second
PII a[N];int siz[N],top;
bool cmp(PII n1,PII n2){return n1.fi<n2.fi;}
signed main()
{
	int n,m,k;cin>>n>>m>>k;
	for(int i=1;i<=n;i++)cin>>a[i].fi>>a[i].se;
	sort(a+1,a+n+1,cmp);
	int ans=0;
	for(int i=1;i<=n;i++)
	{
		while(top<=i-1&&a[i].fi-a[top].fi>=k)m+=siz[top++];
        siz[i]=min(m,a[i].se);
        m-=siz[i];
        ans+=siz[i];
	}
	cout<<ans;
	return 0;
}