#include <fstream>
#include <queue>
#include <algorithm>
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
const int nmax = 100000;
struct ura
{
    int dist, val, t;
}v[nmax + 5];
priority_queue <int> q;
int n, x, l;
bool cmp(ura a, ura b)
{
    return a.t < b.t;
}
int main()
{
    fin >> n >> x >> l;
    int i, tmax = -1;
    for ( i = 1; i <= n; ++i )
    {
        fin >> v[i].dist >> v[i].val;
        v[i].t = (x - v[i].dist ) / l + 1;
    }

    sort ( v + 1, v + n + 1, cmp );
    int p = n;
    long long sol = 0;
    for ( i = v[n].t; i >= 1; --i )
    {
        while ( v[p].t == i )
        {
            q.push(v[p].val);
            --p;
        }
        sol += q.top();
        q.pop();
    }
    fout << sol << '\n';
    return 0;
}