#include <iostream>
#include <fstream>

using namespace std;

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

long long n,s,t,a[100001],d[100001],st=1,dr=0,c;
void stanga(int i)
{
    if(d[st]<i-t)
        ++st;
}
void dreapta(int i)
{
    while(st <= dr && s*(i-d[dr])+a[d[dr]]>=a[i])
        dr--;
    d[++dr]=i;
}
int main()
{
    long long i,S=0;
    in>>n>>s>>t;
    for(i=1; i<=n; i++)
    {
        in>>a[i]>>c;
        dreapta(i);
        stanga(i);
        S=S+c*(s*(i-d[st])+a[d[st]]);
    }
    out<<S;
    return 0;
}