#include<algorithm>
using namespace std;
struct lupu
{
    int d,a;
};
lupu a[100003];
int n,x,l;
int cmp (lupu a,lupu b)
{
    return a.a>b.a || (a.a==b.a && a.d>b.d);
}
void read ()
{
    int i;
    scanf("%d%d%d",&n,&x,&l);
    for(i=1;i<=n;++i)
        scanf("%d%d",&a[i].d,&a[i].a);
}
void solve ()
{
    int i,dist=0,s=0;
    for(i=1;i<=n;++i)
        if(a[i].d+dist<=x)
            s+=a[i].a,dist+=l;
    printf("%d",s);
        
}
int main ()
{
    freopen ("lupu.in","r",stdin);
    freopen ("lupu.out","w",stdout);
    int i,ok,oki;
    read ();
    sort (a+1,a+1+n,cmp);
    solve ();
    return 0;
}