Go: package main

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

func main() {
	io := NewIo()
	defer io.Flush()
	for {
		n, p := io.NextInt(), io.NextInt()
		if n == -1 {
			break
		}
		isPrime := SieveOpt(200000)
		prime := make([]int, p)
		cnt := 0
		if n < 2 {
			prime[0] = 2
			cnt++
		}
		for i := (n + 1) / 2; i < len(isPrime) && cnt < p; i++ {
			if isPrime[i] == true {
				prime[cnt] = 2*i + 1
				cnt++
			}
		}
		comb := make([]int, 0, p*p)
		for i := 0; i < p; i++ {
			for j := i; j < p; j++ {
				comb = append(comb, prime[i]+prime[j])
			}
		}
		sort.Ints(comb)
		io.Println(comb[p-1])
	}
}

func SieveOpt(x int) []bool {
	flags := make([]bool, x/2) // flags[i] := 2*j+1 is prime
	for i := 1; i < x/2; i++ {
		flags[i] = true
	}
	sqrtXi := int(math.Ceil(math.Sqrt(float64(x)))) / 2
	for i := 1; i < sqrtXi; i ++ {
		if !flags[i] {
			continue
		}
		for j := 2 * i * (i + 1); j < x/2; j += 2*i + 1 {
			flags[j] = false
		}
	}
	return flags
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include <stdio.h>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>

using namespace std;


#define NUM 150000

int main(){
	int table[NUM],limit;

	for(int i=0; i < NUM;i++)table[i] = 1;
	table[0] = 0;
	table[1] = 0;

	limit = sqrt(NUM);

	for(int i=2;i<=limit;i++){
		if(table[i] == 1){
			for(int k=2*i;k < NUM; k += i){
				table[k] = 0;
			}
		}
	}

	int prime_table[NUM],index = 0;

	for(int i = 2; i < NUM; i++){
		if(table[i] == 1){
			prime_table[index++] = i;
		}
	}


	int N,P,work[30],calc[465],count;

	while(true){
		scanf("%d %d",&N,&P);
		if(N == -1 && P == -1)break;

		count = 0;

		for(int i = 0; i < index; i++){
			if(prime_table[i] > N){
				work[count] = prime_table[i];
				count++;
				if(count == 30)break;
			}
		}

		count = 0;

		for(int i = 0; i <= 29; i++){
			for(int k = i; k <= 29; k++){
				calc[count++] = work[i] + work[k];
			}
		}

		for(int i = 1; i <= 464; i++){
			for(int k = 464; k >= i; k--){
				if(calc[k] < calc[k-1])swap(calc[k],calc[k-1]);
			}
		}

		printf("%d\n",calc[P-1]);

	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int a[100000]={2,3},i,j,k,c=2,b[100002][101],q,w[450];
int main(){
  for(i=4;i<150000;i++){
    for(k=1,j=2;j*j<=i;j++){
      if(i%j==0){k=0;break;}
    }
    if(k)a[c++]=i;
  }k=0;
  for(i=0;i<=100000;i++){
    if(i>a[k])k++;
    for(q=0,j=k;j<k+20;j++){
      for(c=j;c<j+20;c++){
        w[q++]=a[j]+a[c];
      }
    }
    sort(w,w+q-1);
    for(c=0;c<=100;c++)b[i][c]=w[c];
  }
  while(cin>>i>>j){
    if(i<0)break;
    cout<<b[i][j-1]<<endl;
  }
}