#include <fstream>
#include <deque>
#define NMAX 100005

using namespace std;

ifstream f("branza.in");
ofstream g("branza.out");
long long n, s, t;
long long pmin;
deque<long long> D;
long long c[NMAX], p[NMAX];
int main()
{
    f>>n>>s>>t;
    for(int i=0; i<n; i++){
        f>>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);
        pmin = pmin+c[D.front()]*p[i] + p[i]*(i-D.front())*s;
    }
    g<<pmin;
    return 0;

}