#include <bits/stdc++.h>

using namespace std;

ifstream fin("branza.in");

ofstream fout("branza.out");

deque<long long> d;

long long sol;

int  n, s, t, p[100005], c[100005];

int main()
{
  fin>>n>>s>>t;  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;
}