#include <fstream>
#include <algorithm>
#include <set>
#include <queue>
#define int long long
using namespace std;
ifstream cin("lupu.in");
ofstream cout("lupu.out");
struct oaie
{
    int ture,lana;
} v[100005];
int n,x,l,d;
int sol;
int cmp(oaie a,oaie b)
{
    if(a.ture>b.ture)
        return 1;
    else
        return 0;
}
struct cmp1
{
    int operator()(const int &a,const int &b)
    {
        if(a<b)
            return 1;
        else
            return 0;
    }
};
priority_queue<int,vector<int>,cmp1>q;
signed main()
{
    cin>>n>>x>>l;
    for(int i=1; i<=n; i++)
    {
        cin>>d>>v[i].lana;
        v[i].ture=(x-d)/l;

    }
    sort(v+1,v+n+1,cmp);
    int idx=1;
    for(int i=v[1].ture;i>=0;i--)
    {
        while(idx<=n&&v[idx].ture==i)
        {
            q.push(v[idx].lana);
            idx++;
        }
        if(!q.empty())
        {
            sol=(long long)(sol+q.top());
            q.pop();
        }
    }
    cout<<sol;
    return 0;
}