#include <fstream>
#include <deque>
#include <iostream>
 
using namespace std;
 
long long n, s, t, cost, c[100005], p[100005];
deque<long long> deq;
ifstream f("branza.in");
ofstream g("branza.out");
 
int main()
{
    f>>n>>s>>t; // n saptamani, s cost depozit, t termen expirare
 
    for(int i=0; i<n; i++){
        f>>c[i]>>p[i]; // cost de fabricare, cantitatea cumparata
 
        while(!deq.empty() && (c[deq.back()] + (i-deq.back())*s) >= c[i])
          deq.pop_back();
        while(!deq.empty() && (i-deq.front())>t) 
          deq.pop_front();
 
        deq.push_back(i); 

        cost = cost+c[deq.front()]*p[i] + p[i]*(i-deq.front())*s;
    }
 
    g<<cost;
    return 0;
}