#include <fstream>
#include <algorithm>
#include <queue>
#define Nmax 1000005
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
struct nod
{
    int x, y;
}v[Nmax];
bool cmp(const nod a, const nod b)
{
    return a.x < b.x;
}
int n, k, i, lim, val, s = 0, maxx = 0, d;
priority_queue < int > Q;
int main()
{
    f >> n >> d >> k;
    for(i = 1; i <= n; i++)
        f >> v[i].x >> v[i].y;
    sort(v + 1, v + n + 1, cmp);
    i = 1;
    for(lim = 0; lim <= d && i <= n; lim = lim + k)
    {
        maxx = 0;
        for(i = i; i <= n && v[i].x <= lim; i ++)
                    Q.push(v[i].y);
        if(!Q.empty())
        {
            val = Q.top();
            s += val;
            Q.pop();
        }
    }
    g << s;
    return 0;
}