#include<fstream>
#include<algorithm>
#include<queue>
#define NMAX 100001
using namespace std;
int n,x,l,i,d;
priority_queue<int>q;
struct oaie
{
    int t,l;
}v[NMAX];
bool cmp(oaie a,oaie b)
{
    return (a.t>b.t);
}
int main()
{
    ifstream f("lupu.in");
    ofstream g("lupu.out");
    f>>n>>x>>l;
    for (i=1;i<=n;++i)
    {
        f>>d>>v[i].l;
        if (d<=x) v[i].t=(x-d)/l+1;
    }
    sort(v+1,v+n+1,cmp);
    i=1;
    long long s=0,k;
    for (k=v[i].t;k>0;--k)
    {
        while (i<n && v[i].t==k)
        {
            q.push(v[i].l);
            ++i;
        }
        if (!q.empty()) {s+=q.top();q.pop();}
    }
    g<<s<<"\n";
    return 0;
}