#include <fstream>

using namespace std;
ifstream cin("branza.in");
ofstream cout("branza.out");
int v[100001],dq[100001];
int main()
{
    int n,i,s,t,st=1,dr=0,nrr;
    long long p=0,s2,s1;
    cin>>n>>s>>t;
    for(i=1;i<=n;i++)
    {
      cin>>v[i]>>nrr;
      while(v[i]<v[dq[dr]]+s && dr>0)
        dr--;
      dr++;
      dq[dr]=i;
      while(dq[st]+t<=i )
        st++;
      s2=(long long)v[i]*nrr;
      s1=(long long)v[dq[st]]*nrr;
      s1+=(long long)s*(i-dq[st])*nrr;
      p+=min(s1,s2);
    }
    cout<<p;
    return 0;
}