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

int a[100][100];

void insereaza (int a[100][100], int val, int i, int j) {

	a[0][j] = a[0][j] - a[j][j] + val;
	for (int k=j; k>=i; k--)
		a[k][j] = a[k-1][j];
	a[i][j] = val;
}

void insereaza_gutuie (int a[100][100], int val, int j) {

	if (val < a[j][j]) return;

	if (a[0][j] == 0) {
		a[0][j] = val;
		a[1][j]=val;
		return;
	}
	for (int i=1; i<=j; i++)
		if (val > a[i][j]) {
			insereaza (a, val, i, j);
			break;
		}
}

int main () {

FILE *f, *g;
int i, j, n, hmax, u, a[100][100], s=0, index=0, h, gr, indice=0;

f = fopen ("gutui.in", "r");
g = fopen ("gutui.out", "w");

fscanf (f, "%d", &n);
fscanf (f, "%d", &hmax);
fscanf (f, "%d", &u);


for (i=1; i<=n; i++) {
	fscanf (f, "%d", &h);
	fscanf (f, "%d", &gr);
	j = (hmax-h)/u + 1;
	if (j > indice)
		indice = j;
	insereaza_gutuie (a, gr, j);
}

for (j=1; j<=indice; j++) {
	if (s < a[j][j])
		s = a[0][j];
	else
		s += a[1][j];
}

printf ("%d\n", s);
	

fclose (f); fclose (g);

return 0;
}