#include <fstream>
#include <deque>
using namespace std;
ifstream fin("branza.in");
ofstream fout("branza.out");
deque <int> d;
int n, s, t, c[1000005], p[1000005];
int main()
{
    fin>>n>>s>>t;
    int sol=0;
    for(int i=1;i<=n;++i)
    {
        fin>>c[i]>>p[i];
        while(!d.empty() && c[d.back()]+ (i-d.back())*s>=c[i])
        {
            d.pop_back();
        }
        while(!d.empty() && (i-d.front())>t)
        {
            d.pop_front();
        }
        d.push_back(i);
        sol+=c[d.front()]*p[i]+p[i]*(i-d.front())*s;
    }
    fout<<sol;
    return 0;
}