#include<cstdio>
#include<deque>
using namespace std;
int main()
{
    freopen("branza.in","r",stdin);freopen("branza.out","w",stdout);
    deque<int>d;int n,s,t,v1[100005],v2[100005],i;
    unsigned long long pr=0;
    scanf("%d%d%d",&n,&s,&t);
    for(i=1;i<=n;++i)
    {
        scanf("%d%d",&v1[i],&v2[i]);
        while(!d.empty()&&(i-d.back())*s>v1[i]-v1[d.back()])
            d.pop_back();
        d.push_back(i);
        if(i-t==d.front())
            d.pop_front();
        pr+=v2[i]*v1[d.front()]+(i-d.front())*v2[i]*s;
    }
    printf("%llu",pr);
}