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 <iostream>
using namespace std;
bool prime[200005] = {true};

void init(void){
    prime[0] = false, prime[1] = false;
    for(int i = 2 ; i < 1000 ; i++){
        if(prime[i] == true){
            for(int k = 2 ; i * k < 200005 ; k++){
                prime[i * k] = false;
            }
        }
    }
}

int main(void){
    init();
    for(;;){
        int N, P;
        cin >> N >> P;
        if(N == 0 && P == 0){return 0;}
        int p[15];
        int ptr=0;
        for(int i = N + 1 ; ptr<15 ; i++){
            if(prime[i]){p[ptr] = i; ptr++;}
        }
        int sum[120]; ptr=0;
        for(int i = 0 ; i < 15 ; i++){
            for(int j = i ; j < 15 ; j++){
                sum[ptr] = prime[i] + prime[j]; ptr++;
            }
        }
        for(int i = 0 ; i < 15 ; i++){
            for(int j = i+1 ; j < 15 ; j++){
                if(sum[i] < sum[j]){
                    int temp = sum[i];
                    sum[i] = sum[j];
                    sum[j] = temp;
                }
            }
        }
        cout << sum[P-1] << endl;
    }
}

C++: #include <bits/stdc++.h>
using namespace std;
 
using ll=long long;
#define int ll
 
#define FOR(i,a,b) for(int i=int(a);i<int(b);i++)
#define REP(i,b) FOR(i,0,b)
 
int read(){
    int i;
    scanf("%lld",&i);
    return i;
}
 
bool is_prime(int n){
    if(n==0||n==1) return false;
    if(n==2) return true;
    for(int i=2;i*i<=n;i++){
        if(n%i==0) return false;
    }
    return true;
}
 
signed main(){
    while(true){
        int N=read(),P=read();
        if(N==-1&&P==-1) break;
        vector<int> prime;
        vector<int> matsuzaki;
        while(1){
            if(is_prime(N)){
                prime.push_back(N);
                REP(j,prime.size()){
                    matsuzaki.push_back(prime[j]+N);
                }
                if(prime.size()>=P+100){
                    break;
                }
            }
            N++;
        }
        sort(matsuzaki.begin(),matsuzaki.end());
        cout << matsuzaki[P - 1] << endl;
    }    
}

C++: #include <iostream>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#include <set>
#include <map>

#define MAX 10000000
using namespace std;


int prime[MAX];

bool is_Prime[MAX];

int ans[1010];


int main(){

  for(int i = 2 ; i < MAX ; i++){
    is_Prime[i] = true;
  }

  for(int i = 2 ; i < MAX ; i++){
    if(is_Prime[i]){
      for(int j = 2; i*j < MAX ; j++)
	is_Prime[i*j] = false;
    }
  }

  for(int i = 2,j = 0; i < MAX ; i++){
    if(is_Prime[i] ){
      prime[j] = i;
      j++;
    }
  }

  for(int i = 0; i < 100; i++){
    //  cout << prime[i] << " ";
  
  }

  int N,P;

  while(1){
    cin >> N >> P;
    if(N == -1 && P == -1 ) break;

    int i;
    for(i = 0; prime[i] <= N ;i++){}
    // prime[i] テ」ツ?ッNテ」ツつ暗」ツつ甘・ツ、ツァテ」ツ?催」ツ??、ツクツ?ァツ閉ェテ・ツーツ湘」ツ?陛」ツ?ェテァツエツ?ヲツ閉ー 
    // cout << i << " " ;



    int t,s,x = 0;

    for(int k = i,t = 0 ; t < 40 ; t++,k++){
      for(int l = k,s = k-i ; s < 40 ; s++,l++){
	ans[x] = prime[k]+prime[l];
	//		cout << ans[x] << " ";
	x++;
      }
      //     cout << endl;
    }

    sort(ans ,ans + 500);


    for(i = 0; i < 100 ; i++){
      //    cout << ans[i] << " ";
    }
    //    cout << endl;    
       cout << ans[P-1] << endl;

  }

  return 0;
}