#include<stdio.h>
struct vector
{
	long long c,nr;
};
long long n,s,t,suma,p,u;
vector v[100002];
long long d[100002];

void dreapta(long long i)
{
	while(p<=u && v[i].c<=(v[d[u]].c+s*(i-d[u])))
		u--;
	d[++u]=i;
}

void stanga(long long i)
{
	while((i-d[p])>t)
		p++;
}

void read()
{
	freopen("branza.in","r",stdin);
	freopen("branza.out","w",stdout);
	scanf("%lld%lld%lld",&n,&s,&t);
	long long i;
	for(i=1;i<=n;i++)
		scanf("%lld%lld",&v[i].c,&v[i].nr);
}

void rez()
{
	long long i;
	p=u=1;
	d[1]=1;
	suma=v[d[1]].c*v[1].nr;
	for(i=2;i<=n;i++)
	{
		dreapta(i);
		stanga(i);
		suma=suma+v[d[p]].c*v[i].nr+(i-d[p])*s*v[i].nr;
	}
	printf("%lld\n",suma);
}

int main()
{
	read();
	rez();
	return 0;
}