Problem:
Score : 200 points

Problem Statement

We have held a popularity poll for N items on sale. Item i received A_i votes.

From these N items, we will select M as popular items. However, we cannot select an item with less than \dfrac{1}{4M} of the total number of votes.

If M popular items can be selected, print Yes; otherwise, print No.

Constraints

1 \leq M \leq N \leq 100

1 \leq A_i \leq 1000

A_i are distinct.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M
A_1 ... A_N

Output

If M popular items can be selected, print Yes; otherwise, print No.

Sample Input 1

4 1
5 4 2 1

Sample Output 1

Yes

There were 12 votes in total. The most popular item received 5 votes, and we can select it.

Sample Input 2

3 2
380 19 1

Sample Output 2

No

There were 400 votes in total. The second and third most popular items received less than \dfrac{1}{4\times 2} of the total number of votes, so we cannot select them. Thus, we cannot select two popular items.

Sample Input 3

12 3
4 56 78 901 2 345 67 890 123 45 6 789

Sample Output 3

Yes

Solution in Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
)

type row []string

type data []row

func main() {
	nextReader = newScanner()
	N := nextInt()
	M := nextInt()
	sum := 0
	As := []int{}
	for n := 0; n < N; n++ {
		A := nextInt()
		As = append(As, A)
		sum += A
	}
	sort.Sort(sort.Reverse(sort.IntSlice(As)))
	for n := 0; n < M; n++ {
		if As[n] < sum/(4*M) {
			fmt.Print("no")
			return
		}
	}
	fmt.Print("yes")
}

var nextReader func() string

func newScanner() func() string {
	r := bufio.NewScanner(os.Stdin)
	r.Buffer(make([]byte, 1024), int(1e+11))
	r.Split(bufio.ScanWords)
	// r.Split(bufio.ScanLines)
	return func() string {
		r.Scan()
		return r.Text()
	}
}

func CustomScan(data []byte, atEOF bool) (advance int, token []byte, err error) {
	for i := 0; i < len(data); i++ {
		if data[i] == ' ' {
			return i + 1, data[:i], nil
		}
	}
	fmt.Println(data)
	return 0, data, bufio.ErrFinalToken
}

func nextStrings() func() string {
	r := bufio.NewScanner(os.Stdin)
	r.Buffer(make([]byte, 1024), int(1e+11))
	// r.Split(bufio.ScanWords)
	r.Split(CustomScan)
	return func() string {
		r.Scan()
		return r.Text()
	}
}

func nextString() string {
	return nextReader()
}
func nextInt64() int64 {
	v, _ := strconv.ParseInt(nextReader(), 10, 64)
	return v
}
func nextInt() int {
	v, _ := strconv.Atoi(nextReader())
	return v
}
func nextInts(n int) []int {
	r := make([]int, n)
	for i := 0; i < n; i++ {
		r[i] = nextInt()
	}
	return r
}
func nextInt64s(n int) []int64 {
	r := make([]int64, n)
	for i := 0; i < n; i++ {
		r[i] = nextInt64()
	}
	return r
}
func nextFloat64() float64 {
	f, _ := strconv.ParseFloat(nextReader(), 64)
	return f
}

func maxInt(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}