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

using namespace std;

typedef struct gs{
    unsigned int ng;
    unsigned int gg;
} gs;

unsigned int h,u;
unsigned int n;
gs *gt;
unsigned int *luate;
unsigned int *q /* cate mai pot lua de pe niv. respectiv */;
unsigned int nr_luate = 0;

unsigned int p;

unsigned int gmax = 0;
unsigned int nivmax = 0;
unsigned int nivmin = UINT_MAX;

int compare (const void * a, const void * b)
{
    if( ((gs *)b)->gg != ((gs *)a)->gg ){
        if ( ((gs *)b)->gg > ((gs *)a)->gg ){
            return 1;
        }
        else{
            return -1;
        }
    }
    else{
        if( ((gs *)b)->ng > ((gs *)a)->ng ){
            return 1;
        }
        else
            if ( ((gs *)b)->ng < ((gs *)a)->ng ){
                return -1;
            }
            else{
                return 0;
            }
    }
}

int get_gmax(){
    //cout<<"nivmax = "<<nivmax<<", nivmin = "<<nivmin<<", p = "<<p<<", n = "<<n<<endl;
    //unsigned int j, barrier;
    unsigned int i, j, k, t, y, flag;
    
    //barrier = nivmax + 1;
    
    for(i=0;i<p;i++){
        
                
        //cout<<nr_luate<<endl;
        
        /*
        for(j=0;j<nr_luate;j++){ 
            cout<<"q[j] = "<<q[j]<<", ";
        }
        cout<<endl;*/
        
        if(i==n){
            break;
        }

        k = 0;
        t = 0;
        y = 0;
        flag = 1;
        for(j=0;j<nr_luate;j++){ 
            if(luate[j] > gt[i].ng){
                k++; /* cate s-au luat de "mai sus" */
                //if(q[j]>0){
                    //q[j]--;
                //}
            }
            else {
                if(luate[j] < gt[i].ng){
                    t++; /* cate s-au luat de "mai jos" */
                    if(q[j] == 0){
                        flag = 0;
                    }
                //if(q[j]>0){
                    //q[j]--;
                //}
                }
                else{ /* cele luate de pe nivelul curent */
                    y++;
                    if(q[j] == 0){
                        flag = 0;
                    }
                }
            }
        }
        /*
        TODO:
            -nu pot lua elementul curent daca am luat deja alte elemente care se afla "mai jos" ca el,
            consumandu-i astfel pozitia
        */
        
        //cout<<"nivmax = "<<nivmax<<", gt.ng = "<<gt[i].ng<<", gt.gg = "<<gt[i].gg<<", k = "<<k<<endl;
        
        if( ( nivmax + 1 > ( k + y) + gt[i].ng ) && flag ){// && ( gt[i].ng < barrier ) ){
        //if(nivmax - gt[i].ng - k > 0 ){ //????
            luate[nr_luate] = gt[i].ng;
            //cout<<nr_luate<<"      "<<nivmax  + 1 - gt[i].ng<<endl;
            if( nivmax  + 1 < gt[i].ng + ( k + y) ){
                q[nr_luate] = 0;
            }
            else{
                q[nr_luate] = nivmax  + 1 - gt[i].ng - ( k + y);
            }
            
            //cout<<"--- q = "<<q[nr_luate]<<", k = "<<k<<", y = "<<y<<", ng = "<<gt[i].ng<<endl;
            
            nr_luate++;
            
            for(j=0;j<nr_luate;j++){
                if( gt[i].ng >= luate[j] )
                    if(q[j]>0){
                        q[j]--;
                    }
            }
            //cout<<nr_luate<<"  "<<gt[i].gg<<"  "<<gt[i].ng<<endl;
            
            gmax = gmax + gt[i].gg;
            //cout<<"q = "<<q[nr_luate - 1]<<",   ng = "<<gt[i].ng<<",   g = "<<gt[i].gg<<",   k = "<<k<<",   nivmax = "<<nivmax<<",   n_luate = "<<nr_luate<<endl;
            
            /*
            if( nivmax == ( k + y ) + gt[i].ng ){ //nu mai pot lua nimic de pe acel nivel
                if( gt[i].ng < barrier )
                    barrier = gt[i].ng;
                cout<<"barrier = "<<barrier<<endl;
            }*/
            
            //cout <<"            "<< nivmax + 1 - gt[i].ng - k <<endl;
        }
        else{
            p++;
        }
    }
    
    return 0;
}

int read_vec(){
    ifstream fin;
    unsigned int i, j;
    //int nvc;
    unsigned int hg;
    int f = 1;
    int o;
    
    fin.open("gutui.in",ios::in);
    
    fin>>n;
    fin>>h;
    fin>>u;
    
    o = u - ( h % u ) - 1;
    
    h = h + o;
    
    gt = (gs *)malloc( n * sizeof( gs ));  
    
    nivmax = h / u;
    

    for(i=0;i<n;i++){
        fin>>hg;
        
        fin>>gt[i].gg;
        
        if(hg>h){
            i--;
            n--;
            continue;
        }
        
        hg = hg + o;

        gt[i].ng = hg / u;
        
        if(gt[i].ng < nivmin){
            nivmin = gt[i].ng;
        }
    }  
    
    p = nivmax - nivmin + 1;
    
    if(p > n){ //??
        p = n;
    }
    
    luate = (unsigned int *)malloc( p * sizeof( unsigned int ));
    q = (unsigned int *)malloc( p * sizeof( unsigned 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();  
    
    get_gmax();
    
    write_sol();
    
    //cin.get();//to_comment
        
    return 0;
}