#include<stdio.h>

#define NMAX 100000
struct bee{int d,a,g;};
bee v[NMAX+1];

void poz(int li,int ls,int &piv){
int i=li,j=ls,d=0;
bee aux;
while(i<j){
	if(v[i].a<v[j].a||
	   v[i].a==v[j].a&&v[i].g>v[j].a){
			aux=v[i];v[i]=v[j];v[j]=aux;d=1-d;
			}
	   i+=d;
	   j-=1-d;
	}
piv=i;
}
void qsrt(int st,int dr){
int piv;
if(st<dr){
	poz(st,dr,piv);
	qsrt(st,piv-1);
	qsrt(piv+1,dr);
	}
}


int main(){
freopen("lupu.in","r",stdin);
freopen("lupu.out","w",stdout);
int n,x,l,gmax,rmax;
scanf("%d%d%d",&n,&x,&l);
gmax=x/l+1;
rmax=x%l;
if(rmax==0) rmax=l;
int i,j,k=n;
for(i=0;i<n;++i){
	scanf("%d%d",&v[i].d,&v[i].a);
	if(v[i].d>x) {i--;k--;continue;}
	v[i].g=(x-v[i].d)/l+1;
	}
n=k;
qsrt(0,n-1);
long long s=0L;
int max[NMAX+1]={0},cmmg=1,gr;
for(i=0;i<n&&cmmg<gmax;++i){
	gr=v[i].g;
	if(gr==cmmg){
		if(max[gr]==0) max[gr]=v[i].a;
		}
	else if(cmmg<gr){
		max[cmmg]=v[i].a;
		while(cmmg<=gmax&&max[cmmg]) cmmg++;
		}
	}

for(i=1;i<=gmax;++i)
	s+=max[i];
printf("%lld",s);
return 0;
}