#include <fstream>
#include <deque>
using namespace std;
ifstream fin ("branza.in");
ofstream fout ("branza.out");
long long N, S, T, sum, C[100010], W[100010];
deque < int > Dq;

int main()
{
    fin >> N >> S >> T;
    for (int i=1; i<=N; i++)
    {
        fin >> C[i] >> W[i];
        while (!Dq.empty() && C[i] <= C[Dq.back()] + S)
            Dq.pop_back();
        Dq.push_back(i);

        while (Dq.front() <= i-T) Dq.pop_front();

        sum += C[Dq.front()] * W[i] + S * W[i] * (i - Dq.front());
    }

    fout << sum << '\n';
    fout.close();
    return 0;
}