#include<stdio.h>
#define ll long long
long long sum;
long s,n,t,c[100006],v[100006],a[100006],b[100006],in,sf;
int main()
{
    long i;
    freopen("branza.in","r",stdin);
    freopen("branza.out","w",stdout);
    scanf("%ld%ld%ld",&n,&s,&t);
    for (i=1;i<=n;i++)
    {
        scanf("%ld%ld",&a[i],&b[i]);
        c[i]=a[i]+s*(n-i);
    }
    for (i=1;i<=n;i++)
    {
        while(in<=sf && c[i]<c[v[sf]])
            sf--;
        v[++sf]=i;
        if(in<=sf && v[in]<i-t)
            in++;

        sum=sum+(ll)b[i]*(a[v[in]]+(i-v[in])*s);
    }

    printf("%lld",sum);
return 0;
}