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>
using namespace std;

#define rep(i, n) for(ll i = 0; i < (ll)(n); i++)
typedef long long ll;
bool prime[10000000];
void makePrime(){
  memset(prime,true,sizeof(prime));
  prime[0] = false;
  prime[1] = false;

  for(int i = 0; i * i < 10000000; i++){
    if(prime[i] == false) continue;
    ll x = 2;
    while(x*i < 10000000){
      prime[x*i] = false;
      x++;
    }
  }
}



void solve(ll a, ll b){
  int cnt = 0;
  vector<int> p;
  for(int i = a+1; cnt < 110; i++){
    if(prime[i]){
      p.push_back(i);
      cnt++;
    }
  }
  vector<int> sum;
  rep(i,110){
    for(int j = i; j < 110; j++){
      sum.push_back(p[i]+p[j]);
    }
  }
  sort(sum.begin(), sum.end());
  // rep(i,sum.size()) cout << sum[i] << " ";
  // cout << endl;
  cout << sum[b-1] << endl;
}


int main(){
  ll a,b;
  makePrime();
  while(true){
    cin >> a >> b;
    if(a == -1 && b == -1) break;
    solve(a,b);
  }
  return 0;
}

C++: #include<iostream>
#include<string.h>
#include<string>
#include<sstream>
#include<cstdio>
#include<stdlib.h>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
#include<set>
#define ll long long int
#define ld long double
#define INF 1000000000
#define EPS 0.0000000001
#define rep(i,n) for(i=0;i<n;i++)
using namespace std;
typedef pair<int, int> pii;

int main()
{
  bool prime[1000000]={};
  int i,j,k,l;
  for(i=2;i<1000000;i++)
    if(prime[i]==false)
      for(j=2;i*j<1000000;j++)
	prime[i*j]=true;
  prime[0]=prime[1]=true;

  int n,p;
  while(1){
    cin>>n>>p;
    if(n==-1 && p==-1)break;
    int m[100005]={};
    int num=0;
 
    for(i=n+1;i<1000+n;i++)
      if(prime[i]==false)
	for(j=i;j<1000+n;j++)
	  if(prime[j]==false){
	    m[num]=i+j;
	    num++;
	  }
    sort(m,m+num);
    cout<<m[p-1]<<endl;
  }
}

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)*2-1;;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 <vector>
#include <iostream>
#include <algorithm>
 
using namespace std;
 
bool is_prime(int n, int k = 3)
{
    if(n < k * k) { return true; }
     
    if(n % k == 0) { return false; }
     
    return is_prime(n, k + 2);
}
 
int main()
{
    vector<int> prime = {2};
     
    for(int i = 3; i < 101300; i += 2)
    {
        if(is_prime(i))
        {
            prime.push_back(i);
        }
    }
     
    int n, m;
     
    while(true)
    {
        scanf("%d", &n);
        scanf("%d", &m);
         
        if(n == -1 && m == -1) { break; }
         
        int ptr = distance(prime.begin(), lower_bound(prime.begin(), prime.end(), n + 1));
         
        vector<int> c; int r = min(22, m / 2 + 1) - 1;
        
        for(int i = ptr + r; i >= ptr; i--)
        {
            for(int j = ptr + r; j >= i; j--)
            {
                c.push_back(prime[i] + prime[j]);
            }
        }
        
        sort(c.begin(), c.end());
         
        printf("%d\n", c[m - 1]);
    }
     
    return 0;
}

C++: #include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
vector<int> pr;
const int c=1e6;
bool prime[c+1];
void makeprime(){
	for(int i=2;i<=c;i++) prime[i]=true;
	for(int i=2;i*i<=c;i++) if(prime[i]) for(int j=2;j*i<=c;j++) prime[i*j]=0;
	rep(i,c) if(prime[i]) pr.push_back(i);
}
int main(){
	makeprime();
	while(true){
		int n,p;
		scanf("%d%d",&n,&p);
		if(n==-1) break;
		int f=upper_bound(pr.begin(),pr.end(),n)-pr.begin();
		vector<int> ans;
		rep(i,100) rep(j,i+1) ans.push_back(pr[f+i]+pr[f+j]);
		sort(ans.begin(),ans.end());
		printf("%d\n",ans[p-1]);
	}
}