#include <stdio.h>
#include <vector>
#include <iterator>
#include <set>
#include <deque>
using namespace std;

#define f "lupu.in"
#define out "lupu.out"

int val[100001], timp[100001];

struct Functor {
       bool operator () (int i, int j)
       {
            return val[i] > val[j];
       }
};

vector< vector<int> > ts;
multiset<int, Functor> s;
int n, d, t;

int main()
{
    int tmax=0, x;
    freopen(f,"r",stdin);
    freopen(out,"w",stdout);

    scanf("%d%d%d",&n,&t,&d);

    for ( int i = n; i > 0; --i )
    {
        scanf("%d%d",&x,&val[i]);

        if ( x > t ) timp[i] = -1;
        else
        {
             timp[i] = (t-x)/d;
        }

        if ( tmax < (t-x)/d ) tmax = (t-x)/d;
    }

    ts.resize(tmax+1);

    for ( int i = n; i > 0; --i )
    {
        if ( timp[i] != -1 ) ts[timp[i]].push_back(i);
    }

   /* for ( int i = 1; i < ts.size(); i++ )
    {
        if ( ts[i].size() != 0 )
        {
             sort(ts[i].begin(),ts[i].end());
        }
    }*/

    long long maxim=0;

    for ( int j = tmax; j >= 0; --j )
    {
        if ( ts[j].size() != 0 )
        {
             for ( int i = ts[j].size()-1; i >= 0; --i )
             {
                 s.insert(ts[j][i]);
             }
        }
        maxim += val[*s.begin()];
        s.erase(s.begin());
    }

    printf("%lld",maxim);
}