#include <fstream>
#include <algorithm>

using namespace std;
ifstream fin ("lupu.in");
ofstream fout("lupu.out");
pair<int, int> v[100010];
int i,l,x,n,ok,aux,t[100010];
long long sum;

int cmp(pair<int, int> a , pair<int, int> b)
{
    if(a.first!=b.first)
        return a.first>b.first;
    else
        return a.second>b.second;
}

int main ()
{
    fin>>n>>x>>l;
    for(i=1;i<=n;i++)
        fin>>v[i].second>>v[i].first;
    sort(v+1 , v+1+n,cmp);
    for(i=1;i<=n;i++)
    {
        aux=v[i].second;ok=0;
        while(x>=aux)
        {
            ok++;
            aux+=l;
        }
        t[i]=ok;
    }
    ok=0;
    for(i=1;i<=n;i++)
    {
        if(ok<t[i])
        {
            sum+=v[i].first;
            ok++;
        }
    }
    fout<<sum;
    fin.close();
    fout.close();
    return 0;
}