# include <fstream>
# include <deque>
# include <algorithm>
using namespace std;
ifstream f("branza.in");
ofstream g("branza.out");
deque <int> dequ;
int i,j,n,m,S,T;
int c[100005], p[100005];
long long total;
int main ()
{
    f>>n>>S>>T;

    for (i=1; i<=n; ++i)
    {
        f>>c[i]>>p[i];
        while (! dequ.empty() && c[i]<=c[dequ.back()]+S*(i-dequ.back()))
             dequ.pop_back();

        dequ.push_back(i);
        if (dequ.front()<i-T) dequ.pop_front();
        total+=(p[i]*c[dequ.front()]+S*p[i]*(i-dequ.front()));
    }
    g<<total<<"\n";
    return 0;
}