#include <iostream>
#include <fstream>
#include <stdlib.h>

using namespace std;

typedef struct gs{
    int hg;
    int gg;
    //int ig;
} gs;


int n,h,u;
gs *gt;
int * luate;
int nr_luate = 0;

int p;


int gmax = 0;
int nivmax = 0;
int nivmin = 100000;

int compare (const void * a, const void * b)
{
    return ( ((gs *)b)->gg - ((gs *)a)->gg);
}

int print_niv(int **a, int *b){
    int i,j;
    cout<<endl;
    for(i=nivmax;i>=0;i--){
        cout<<i<<".  ";
        for(j=0;j<b[i];j++){
            cout<<a[i][j]<<" ";
        }
        cout<<endl;
    }
    cout<<endl;
    return 0;
}

int get_gmax(){
    //cout<<"nivmax = "<<nivmax<<", nivmin = "<<nivmin<<", p = "<<p<<endl;
    int i,j;
    int k;
    for(i=0;i<p;i++){
        k = 0;
        for(j=0;j<nr_luate;j++){
            if(luate[j] >= gt[i].hg){
                k++;
            }
        }
        
        if(nivmax + 1 - gt[i].hg - k > 0 ){
            luate[nr_luate++] = gt[i].hg;
            gmax = gmax + gt[i].gg;
        }
        else{
            p++;
        }
    }
    
    return 0;
}

int read_vec(){
    ifstream fin;
    int i,last=0;
    
    fin.open("gutui.in",ios::in);
    
    fin>>n;
    fin>>h;
    fin>>u;
    
    gt = (gs *)malloc( n * sizeof( gs ));  
    
    nivmax = h/u + ((h%u == 0)?0:1);
    //cout<<"n = "<<n<<"   h = "<<h<<"   u = "<<u<<endl;
    //cout<<"g = "<<nivmax<<endl;


    for(i=0;i<n;i++){
        fin>>gt[i].hg;
        fin>>gt[i].gg;
        
        gt[i].hg = (gt[i].hg / u) + ( (gt[i].hg % u == 0) ? 0 : 1 ) ;
        if(gt[i].hg <nivmin){
            nivmin = gt[i].hg;
        }
    }  
    
    p = nivmax - nivmin + 1;
    
    luate = (int *)malloc( p * sizeof( int ));
    
    qsort (gt, n, sizeof(gs), compare);
    
    
    fin.close();
    return 0;
}


int write_sol(){
    ofstream fout;
    fout.open("gutui.out",ios::out);
    
    fout<<gmax;
    
    fout.close();
    return 0;
}

int main(){
     
    read_vec();
    //print_mat(m);
    
    //det_maxp();
    //print_mat(m);
    
    //read_mat();
    
    //det_maxr();
    //print_mat(m);
    
    //print_vec(hg);
    //print_vec(gt);
    
    
    get_gmax();
    
    write_sol();
    
    //cout<<"gmax ="<< gmax;

    //print_mat(mr);
    //cout<<"lp= "<<lp<<"  np= "<<np<<endl;
    //cout<<"lr= "<<lr<<"  nr= "<<nr<<endl;
    
    //cin.get();//to_comment
        
    return 0;
}