#include <fstream>
#include <deque>
#define N 10000000

using namespace std;

deque <int> q;
long long c[N], b[N];

int main()
{
    ifstream f("branza.in");
    ofstream g("branza.out");
    long long n, s, t, ss = 0;
    f >> n >> s >> t;
    for (int i = 1;i <= n;++i)
    {
        f >> c[i] >> b[i];
        while (!q.empty() && i - q.front() > t) q.pop_front();
        while (!q.empty() && (i - q.back()) * s * b[i] + c[q.back()] * b[i] > c[i] * b[i]) q.pop_back();///am gasit un pret mai bun
        q.push_back(i);
        ss = ss + (i - q.front()) * s * b[i] + c[q.front()] * b[i];
    }
    g << ss;
    f.close();
    g.close();
    return 0;
}