#include <bits/stdc++.h>
#define pii pair<int,int>
using namespace std;

ifstream fin("lupu.in");
ofstream fout("lupu.out");

vector <pii> v;

bool cmp(pii a,pii b)
{
    return a.first > b.first;
}

int main()
{
    int n,x,L,lana = 0;
    fin >> n >> x >> L;
    for (int i = 0; i< n; i++)
    {
        int a,b;
        fin >> a >> b;
        v.push_back({a,b});
    }
    sort(v.begin(),v.end(),cmp);
   // for (auto a:v)
       // cout << a.first << " " << a.second << "\n";
    set <pair <int,int>> Q;
    int d = v[0].first - L;
    int i = 0;
    while (v[i].first > d && i < n)
    {
        Q.insert({v[i].second,v[i].first});
        if (v[i+1].first <= d || i == n-1)
        {
            lana += Q.rbegin()->first;
            d -= L;
            Q.clear();
        }
        i++;
    }
    fout << lana;
    return 0;
}