#include <fstream>
#include <algorithm>

using namespace std;

ifstream f("lupu.in");
ofstream g("lupu.out");
pair<int, int> v[100005];
int n, x, l;

int main()
{
    f>>n>>x>>l;
    int d, c;
    for(int i = 1; i<=n; i++)
    {
        f>>d>>c;
        v[i] = {d, c};
    }

    sort(v+1, v+n+1);

    /*for(int i = 1; i<=n; i++)
    {
        g<<v[i].first<<" "<<v[i].second<<'\n';
    }*/

    int xmax;
    int i = n;
    int ans = 0;
    while(x >= 0)
    {
        xmax = 0;
        while(i >= 1 && v[i].first >= x-l+1)
        {
            xmax = max(xmax, v[i].second);
            i--;
        }

        ans += xmax;
        x-= l;
    }

    g<<ans;

    return 0;
}