import java.util.*;

public class StepikAlgorithms {
    public static void main(String[] args){

        Scanner input = new Scanner(System.in);

        int thingsNumber = input.nextInt();
        int bagCapacity = input.nextInt();

        Bag bag = new Bag(bagCapacity);

        ArrayList<Thing> things = new ArrayList<>();
        for(int i = 0; i < thingsNumber; i++ ){
            int cost = input.nextInt();
            int weight = input.nextInt();
            things.add(new Thing(cost, weight));
        }
        Collections.sort(things, new Comparator<Thing>(){
            public int compare(Thing t1, Thing t2){
                return Float.compare(t2.specificCost, t1.specificCost);
            }
        });

        for(Thing thing:things){
            if(bag.freeCapacity > thing.weight){
                bag.freeCapacity -= thing.weight;
                bag.summaryCost += thing.cost;
            }else{
                bag.summaryCost += bag.freeCapacity * thing.specificCost;
                break;
            }
        }
        System.out.printf("%.3f",bag.summaryCost);
    }
}

class Thing{
    int cost;
    int weight;
    float specificCost;

    Thing(int cost, int weight){
        this.cost = cost;
        this.weight = weight;
        specificCost = (float) cost / weight;
    }
}

class Bag{
    int freeCapacity;
    double summaryCost;

    Bag(int capacity){
        this.freeCapacity = capacity;
        summaryCost = 0;
    }
}