#include <cstdio>
#include <bitset>
#include <iostream>
#include <fstream>
#define MAXN 100000
#define MAXK 200000
using namespace std;
ifstream f("branza.in");
ofstream g("branza.out");
long long int cost[100005],deq[100005],n,s,t,cap=0,coada=1,pi;
long long sol=0;


int main() {
f>>n>>s>>t;
for(int i=1;i<=n;i++)
{
    f>>cost[i]>>pi;

    while(cap>=coada&&cost[i]<=cost[deq[cap]]+(i-deq[cap])*s)
    {
        cap--;

    }
    deq[++cap]=i;
     while(i-deq[coada]>t&&coada<=cap) ++coada;

    sol=sol+pi*(i-deq[coada])*s+pi*cost[deq[coada]];



}
g<<sol;

}