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;
typedef priority_queue<int, vector<int>, greater<int> > pque;

int np[160000] = {-1, -1, 0};
int primes[14684];

int main()
{
    for(int p=2; p<400; p++)
    {
        if(!np[p])
        {
            for(int i=2*p; i<160000; i+=p)
            {
                np[i] = -1;
            }
        }
    }

    int idx=0;
    for(int i=0; i<160000; i++)
    {
        if(!np[i])
        {
            np[i] = idx;
            primes[idx++] = i;
        }
    }

    int n, p;
    while(cin >> n >> p, ~(n&p))
    {
        pque q;
        n++;
        while(np[n]==-1) n++;
        int pidx = np[n];
        for(int i=0; i<200; i++)
        {
            for(int j=i; j<200; j++)
            {
                q.push(primes[pidx+i] + primes[pidx+j]);
            }
        }
        for(int i=1; i<p; i++) q.pop();
        cout << q.top() << endl;
    }

}

C++: #include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>
using namespace std;

const int N=200000;

int main(void){
	vector<bool> isprime(N+1);
	for(int i=0;i<isprime.size();i++) isprime[i]=true;
	int upto = (int)sqrt(isprime.size());
	isprime[0]=isprime[1]=false;
	for(int i=2;i<=upto;++i){
		if(isprime[i]){//消されてなければその倍数を消す
			for(int j=2;i*j<isprime.size();++j) isprime[i*j] = false;
		}
	}
  
	int n,p;
	while(cin>>n>>p,!(n==-1&&p==-1)){
    vector<int> tmp,ans;
    for(int i=n+1,count=0;count<100;++i){
      if(isprime[i]){
     	 tmp.push_back(i);
     	 ++count;
      }
    }
    for(int i=0;i<100;++i){
      for(int j=i;j<100;++j){
        ans.push_back(tmp[i]+tmp[j]);
      }
    }
    sort(ans.begin(),ans.end());
		cout<<ans[p-1]<<endl;
	}
  return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <memory.h>
#include <queue>
#include <cstdio>
#include <cstdlib>
#include <map>
#include <cmath>
using namespace std;

#define rep(i, n) for(int i = 0; i< n; i++)
typedef long long ll;
typedef pair<int, int> P;

bool isprime(int n){
  if(n == 0 || n == 1) return false;
  for(int i = 2; i * i <= n; i++){
    if(n % i == 0) return false;
  }
  return true;
}

int main(){
  int N, p;
  while(cin >> N >> p && (N != -1 || p != -1)){
    vector<int> primes;
    vector<int> nums;
    while(primes.size() < 100){
      if(isprime(++N)) primes.push_back(N);
    }
    rep(i, (int)primes.size())rep(j, i + 1){
      nums.push_back(primes[i] + primes[j]);
    }
    sort(nums.begin(), nums.end());
    cout << nums[p-1] << endl;
  }
  return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main(){
  bool num[160001] = {false};
  num[0] = num[1] = true;
  for(int i=2; i<401; i++){
    if(num[i] == false){
      for(int j=i*i; j<160001; j+=i){
	num[j] = true;
      }
    }
  }
  vector<int> tag;
  for(int i=0; i<160001; i++){
    if(!num[i]){tag.push_back(i);}
  }
  int n,p;
  while(cin >>n>>p){
    if(n == -1 && p == -1){break;}
    int at = 0;
    vector<int> add;
    for(int i=0;;i++){if(tag[i]>n){at = i;break;}}
    for(int i=at,x=0;i<at+100;i++){
      for(int j=i;j<at+100;j++){
	add.push_back(tag[i]+tag[j]);
      }
    }
    sort(add.begin(),add.end());
    cout<<add[p-1]<<endl;
  }
  return 0;
}