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 <bits/stdc++.h>
#define MAX 222222
using namespace std;
bool is_prim[MAX];

bool isPrim(int x){
  for(int i=2; i < sqrt(x); i++){
    if(x % i == 0)
      return false;
  }
  return true;
}

void init(void){
  for(int i=0; i < MAX; i++){
    is_prim[i] = true;
  }
  is_prim[0] = false;
  is_prim[1] = false;
  for(int i=2; i < MAX; i++){
    for(int j=i+i; j < MAX; j+=i){
      is_prim[j] = false;
    }
  }
}

int main(void){
  int N, P;
  init();
  while(cin >> N >> P, !(N == -1 && P == -1)){
    list<int> seq;
    //int i = 1;
    //while(P > 0){
    //  if(is_prim[i+N]){
    //    seq.insert(seq.end(), i+N);
    //    i++;
    //    P--;
    //  }else{
    //    i++;
    //  }
    //}
    for(int i=1;; i++){
      if(is_prim[i+N]){
        for(int j=i;; j++){
          if(is_prim[j+N]){
            seq.insert(seq.end(), i+N+j+N);
            if(j+N > max(N*10, P*10)) break;
          }
        }
        if(i+N > max(N*10, P*10)) break;
      }
    }
    seq.sort();
    list<int>::iterator it = seq.begin();
    for(int i=1; i < P; i++){
      ++it;
    }
    cout << *it << endl;
  }
  return 0;
}

C++: #include<stdio.h>
int prime[1300001];

void isprime(void){
    int i,j,n,c;

    for(i = 4;i<1300001;i += 2)prime[i] = 1;

    for (i = 3;i * i <= 1300001;i += 2){
        if (prime[i] == 0){
            for (j = i + i; j <= 1300001; j += i){
                prime[j] = 1;
            }
        }
    }
}

int main(void){
    int n,i,a=0;
    int flag,p,j,k;
    isprime();
    
    while (scanf("%d%d",&n,&p),n==-1&&p==-1){
a=0;
flag=0;
        for(i = (n+1)*2;;i++){
for(j = n+1;j < i;j++){
 for(k = j;j+k <= i;k++){
  if(j+k == i){
   if(prime[j]&&prime[k]){
    a++;
    if(a==p){
     printf("%d\n",i);
flag=1;
break;
    }
   }
  }
if(flag)break;
 }
if(flag)break;
}
if(flag)break;
        }
    }
     
    return 0;
}

C++: #include "bits/stdc++.h"
#include<unordered_map>
#pragma warning(disable:4996)
using namespace std;

bool primes[1000000];
bool isso(long long int a) {
	if (a == 1 || a == 0)return false;
	for (long long int i = 2; i*i <= a; ++i) {
		if ((a%i)) {
		}
		else {
			return false;
		}
	}
	return true;
}
int main() {
	for (int i = 0; i < 1000000; ++i) {
		primes[i] = isso(i);
	}
	while (1) {
		int N, P; cin >> N >> P;
		if (N == -1)break;
		vector<int>aset;
		for (int i = N + 1; i < N + 1000; ++i) {
			for (int j = i; j < N + 1000; ++j) {
				if (primes[i] && primes[j]) {
					aset.emplace_back(i + j);
				}
			}
		}
		sort(aset.begin(), aset.end());
		cout << aset[P - 1] << endl;
	}
	return 0;
}

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;
        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 <algorithm>
#include <cstdio>
#include <iostream>
using namespace std;

int main(){
	bool prime[200000];
	long p[20000]; //素数が小さい順に入っている
	p[0]=2;
	
	for(long i=0; i<200000; ++i) prime[i]=true;
	prime[0]=prime[1]=false;
	for(long i=0; i<200000; ++i){
		if(prime[i])
			for(long j=2; i*j<200000; ++j) prime[i*j]=false;
	}
	
	long c=1; 
	for(long i=3; i<200000; i+=2){
		if(prime[i]) p[c++]=i;
	}
	
	//printf("c=%ld", c);
	
	while(1){
		long n;
		int q;
		long m[15000];
		
		scanf(" %ld %d", &n, &q);
		if(n==-1 && q==-1) break;
		
		int count=0;
		long t=0;
		
		while(p[count] <= n) ++count;
		
		for(long i=count; i<count+100; ++i){
			for(long j=i; j<count+100; ++j){
				m[t++]=p[i]+p[j];
			}
		}
		sort(m, m+t);
		printf("%ld\n", m[q-1]);
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main(){
  while(1){
    int n,p;
    vector <int>an;
    int so[101];
    cin>>n>>p;
    if(n==-1&&p==-1)break;
    int c=0;
    for(int i=n+1;c<=p;i++){
      int f=0;
      if(i==1)continue;
      for(int j=2;j*j<=i;j++){
	if(i%j==0){f=1;break;}
      }
      if(f==0){so[c]=i;c++;}
    }
    for(int i=0;i<p;i++)
      for(int j=i;j<p;j++)
	an.push_back(so[i]+so[j]);
    sort(an.begin(),an.end());
    cout<<an[p-1]<<endl;
  }
  return 0;
}