import java.util.*;
public class Main
{
    public static void main(String[] args) throws Exception {
       Scanner s = new Scanner(System.in);
       int n = s.nextInt();
       int t = s.nextInt();
       int[][] mv = new int[n + 1][2];
       for (int i = 1;i<=n;i++)
           for (int j = 0;j<2;j++)
           {
               mv[i][j] = s.nextInt();
           }
       Arrays.sort(mv, 1, n + 1, new Comparator<int[]>() {
           @Override
           public int compare(int[] o1, int[] o2) {
               int s1 = o1[1]/o1[0];
               int s2 = o2[1]/o2[0];
               return s2-s1;
           }
       });
        double sum = 0;
        for (int i = 1;i <= n ;i++)
        {
            if(t > 0)
            {
                if (t>=mv[i][0])
                    sum += mv[i][1];
                else
                    sum += (double) (mv[i][1]/mv[i][0]) * t;

            }
            else
                break;
            t-=mv[i][0];
        }
        System.out.printf("%.2f",sum);
    }
}