#include <fstream>
#include <iostream>
#include <deque>
using namespace std;

ifstream in("branza.in");
ofstream out("branza.out");

deque<long long int> DQzi,DQcost;

int main()
{
    int zile,taxa,stric;
    long long int sol=0;
    in>>zile>>taxa>>stric;

    for(int i=1;i<=zile;i++)
    {
        int cost,cant;
        in>>cost>>cant;

        while(DQzi.empty()==0 && cost<=(i-DQzi.back())*taxa+DQcost.front())
        {
            DQzi.pop_back();
            DQcost.pop_back();
        } /// Elimin ce e mai prost decat ziua curenta
        while(DQzi.empty()==0 && i-DQzi.front()>stric)
        {
            DQzi.pop_front();
            DQcost.pop_front();
        } /// Elimin ce e stricat
        DQzi.push_back(i);
        DQcost.push_back(cost);
        /// Adaug in deque ziua curenta

        sol=sol+cant*((i-DQzi.front())*taxa+DQcost.front());

    }
    out<<sol;

}