#include <bits/stdc++.h>

using namespace std;

ifstream fin("branza.in");

ofstream fout("branza.out");

deque <long long> d;

long long n, s, t, c[1000005], p[1000005];

int main()
{

    fin>>n>>s>>t;

    long long sol=0;

    for(int i=1;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);

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


    }

    fout<<sol;

    return 0;
}