#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

ifstream fin("branza.in");
ofstream fout("branza.out");
deque <int>deq;
long long n,k,c[100005],p[100005],s,t;
long long sum=0;
int main()
{
    cin>>n>>s>>t;
    for(int i=1;i<=n;i++)
    {
        cin>>c[i]>>p[i];
    }
    for(int i=1;i<=n;i++)
    {
        long long cost_rel=c[i]-s*i;
        while(!deq.empty() && c[deq.back()]-s*deq.back()>=cost_rel)
            deq.pop_back();
        deq.push_back(i);
        if(deq.front()<i-t)
            deq.pop_front();
        sum+=(c[deq.front()]+s*(i-deq.front()))*p[i];

    }
    cout<<sum;
    return 0;
}