#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;

}