#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
int n,x,l,ct;
struct oaie
{ int d,b;

};
bool cp(oaie a1,oaie a2)
{
    if(a1.b==a2.b)
        return a1.d<a2.d;
    else return a1.b>a2.b;
}
long long sum;
oaie a[100005];
int main()
{
    fin>>n>>x>>l;
    int i;
    for(i=1;i<=n;++i)
        fin>>a[i].d>>a[i].b;
    sort(a+1,a+n+1,cp);
    for(i=1;i<=n;++i)
        if( 1LL*a[i].d+ct*l <=x)
    { ++ct;
        sum+=a[i].b;
    }
    fout<<sum;
    return 0;
}