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

using namespace std;

deque<long long> d;

ifstream fin("branza.in");
ofstream fout("branza.out");

int main()
{
    long long n, s, t, cost, c[100005], p[100005];

    fin >> n >> s >> t;

    cost=0;

    for (int i = 0; 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);

        cost = cost + c[d.front()] * p[i] + p[i] * (i - d.front()) * s;
    }

    fout << cost;

    fin.close();
    fout.close();
    return 0;
}