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#include <iostream>
#include <fstream>
#include <vector>
#include <deque>
using namespace std;
int n,s,t;
vector<pair<long long,long long>> v;
deque<int> dq;
int main()
{
    ifstream f("branza.in");
    ofstream g("branza.out");
    f>>n>>s>>t;
    for(int i=1; i<=n; i++)
    {
        long long x,y;
        f>>x>>y;
        v.push_back({x,y});
    }
    long long sum=0;
    for(int i=0; i<n; i++)
    {
        long long cost=v[i].first-s*i;
        while(!dq.empty() && v[dq.back()].first-s*dq.back()>=cost)
        {
          dq.pop_back();
        }
       dq.push_back(i);
        if (dq.front() <i - t)
        {
            dq.pop_front();
        }
         sum+=(v[dq.front()].first+s*(i-dq.front()))*v[i].second;
        //cout<<sum<<" "<<v[dq.back()].first<<endl;
    }
    g<<sum;

    return 0;
}