#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

class Gutuie{
    public:
        unsigned int greutate, nivel;
};

bool comp1(Gutuie a, Gutuie b){
    if( a.nivel < b.nivel )
        return false;
    else
        if( a.nivel == b.nivel ){
            if( a.greutate > b.greutate )
                return true;
            else
                return false;
        }
        else
            return true;
}

bool comp2(unsigned int a, unsigned int b){
    return a > b;
}

inline unsigned int nivel( unsigned int a, unsigned int u, unsigned int hmax ){
    if( a % u <= hmax % u )
        return a / u;
    else
        return a / u + 1;
}

int main(){
    unsigned int n, u, hmax;
    ifstream fin("gutui.in");
    ofstream fout("gutui.out");
    fin >> n >> hmax >> u;
    unsigned int i, x, y;
    vector<Gutuie> v(n);
    for(i = 0; i < n; i++){
        fin >> x >> y;
        v[i].greutate = y;
        v[i].nivel = nivel(x, u, hmax);
    }
    sort( v.begin(), v.end(), comp1 );
    unsigned int nivmax = nivel(hmax, u, hmax), niv = v[0].nivel, nr = 0;
    unsigned int gmax = 0;
    vector<unsigned int> greutate;
    for(i = 0; i < n; i++){
        if( v[i].nivel == niv ){
            if( nr < nivmax - niv + 1 ){
                nr ++;
                if( greutate.size() < nivmax - niv + 1 ){
                    gmax += v[i].greutate;
                    greutate.push_back( v[i].greutate );
                    push_heap( greutate.begin(), greutate.end(), comp2 );
                }
                else
                    if( greutate.front() < v[i].greutate ){
                        gmax -= greutate.front();
                        gmax += v[i].greutate;
                        pop_heap( greutate.begin(), greutate.end(), comp2 );
                        greutate.pop_back();
                        greutate.push_back( v[i].greutate );
                        push_heap( greutate.begin(), greutate.end(), comp2 );
                    }
            }
        }
        else{
            niv = v[i].nivel;
            nr = 0;
            i --;
        }
    }
    fout << gmax;
    fin.close();
    fout.close();
    return 0;
}