#include <fstream>
#include <queue>

using namespace std;

ifstream f("lupu.in");
ofstream g("lupu.out");

vector< priority_queue<long> > C;

priority_queue<long> T;

int main()
{
    long N,X,L,D,A;

    f>>N>>X>>L;

    unsigned c;

    for(int i=0;i<N;i++)
    {
        f>>D>>A;
        if(D<=X)
        {
            c=D/L;
            while(C.size()<=c) C.push_back(T);
            C[c].push(A);
        }
    }

    long long sum=0;

    for(int i=0;i<C.size();i++)
    {
        if(!C[i].empty())sum+=C[i].top();
    }

    g<<sum;

    return 0;
}