#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int N ;
int H , U;

typedef struct gutui
		{
		int *g;
		int nr;
		} GUTUI;
GUTUI *G;
int nr_nivele;
int nivel( int h )
{
if ( h % U != 0)
	{
	if ( ( H / U - h / U - 1 ) > nr_nivele ) 
		nr_nivele = ( H / U - h / U - 1 );
	return ( H / U - h / U - 1);
	}
	else
	{
	if ( ( H / U - h / U ) > nr_nivele ) 
		nr_nivele = ( H / U - h / U );
	return ( H / U - h / U );
	}
}

void citire()
{
int i , h , gre , niv , n ;
nr_nivele = 0;
FILE *f = fopen ( "gutui.in" , "r" ) ;
fscanf( f , "%d%d%d", &N , &H , &U) ;
G = ( GUTUI * ) malloc ( ( H / U + 1 ) * sizeof ( GUTUI ) ) ;
if ( H % U != 0)
	H = ( ( H / U ) + 1 ) * U ;
for ( i = 0 ; i < H / U ; i++ )
	{
	G[i].g = ( int * ) malloc ( 10000 * sizeof ( int ) ) ;
	G[i].g[0] = 0;
	G[i].nr = 0;
	}

for ( i = 0 ; i < N ; i++ )
	{
	fscanf ( f , "%d%d" , &h , &gre ) ;
	niv = nivel ( h );
	n = G[niv].nr;
	G[niv].g[n] = gre;
	G[niv].nr = G[niv].nr + 1;
	}
nr_nivele++;

fclose ( f );
}

int compar (const void * x, const void * y) 
{
  return ( * ( int * ) y - * ( int * ) x );
}

void rezolva()
{
FILE *f = fopen ( "gutui.out" , "w" ) ;
int suma = 0;
int i , j , k , l = 0;
int *max = (int *) malloc (10000 * sizeof ( int ) );
for (i = 0 ; i < nr_nivele ; i++) 
	qsort ( G[i].g , G[i].nr , 4 , compar );
for (i = 0 ; i < nr_nivele ; i++) 
	{
	j = i + 1;
	if (G[i].nr != 0) 
		{
		for (k = 0 ; k < j ; k++) 
			if ( ( G[i].nr - k ) > 0 ) 
				{
				max[l] = G[i].g[k];
				l++;
				}
				else
				break;
			qsort ( max , l , 4 , compar );
			if (l > j) 
				l = j;
		}
	}
for ( i = 0 ; i < l ; i++)
	suma = suma + max[i];
fprintf ( f , "%d\n" , suma );
fclose(f);
}

int main()
{
citire();
rezolva();
return 0;
}