#include <fstream>
#include <deque>
using namespace std;
long long n, s, t, cost, c[100005], p[100005];
deque<long long> d;

int main() {
    ifstream fin("branza.in");
    ofstream fout("branza.out");
    fin >> n >> s >> t;
    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;
    return 0;
}