#include <fstream>
#include <deque>

using namespace std;

ifstream f("branza.in");
ofstream g("branza.out");

long long n, s, t, pierd;
deque<long long> v;
long long c[100001], p[100001];
int main()
{
    f>>n>>s>>t;
    for(int i=0; i<n; i++){
        f>>c[i]>>p[i];
        while(!v.empty() && c[v.back()] + (i-v.back())*s >= c[i])
            v.pop_back();
        while(!v.empty() && (i-v.front())>t)
            v.pop_front();
        v.push_back(i);
        pierd = pierd+c[v.front()]*p[i] + p[i]*(i-v.front())*s;
    }
    g<<pierd;

    f.close();
    g.close();

    return 0;

}