import java.util.*;
public class CPU_SCHEDULING{

     public static void main(String []args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int temp = n;
        ArrayList<Node> ar = new ArrayList<>();
        while(n-->0)
        {
            Node nd = new Node(sc.nextInt(),sc.nextInt());
            ar.add(nd);

        }

        Collections.sort(ar,new Sort());


   long sum = 0;
   long length = 0;
   for(Node x : ar)
    {
        length = length + x.l;
        sum = sum + x.w * ( length);
    }

    System.out.println(sum);
}
}


class Node{
    int w,l;
    float dif;
    Node(int w,int l)
    {
        this.w = w;
        this.l = l;
        dif = (float)w / (float)l;
    }

    public String toString()
    {
        return this.w+" "+this.l+" "+this.dif;
    }

}

class Sort implements Comparator<Node>
{

     public int compare(Node a , Node b)
    {
        if(a.dif - b.dif != 0)
           return (int)Math.signum(b.dif - a.dif);
        else return (int)Math.signum(b.w - a.w);

    }

}