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>
#include<cstdio>
#include<algorithm>

using namespace std;

#define NMAX 100

int main(){

	int hurui[20000]={0};
	int prime[10000];
	int table[200000]={0};
	int cnt=0;
	int cou;

	hurui[0]=1,hurui[1]=1;
	for(int i=2;i<20000;i++){
		if(hurui[i]==0){
			prime[cnt]=i;
			cnt++;
			for(int j=i;j<20000;j+=i){
				hurui[j]=1;
			}
		}
	}

	cou=cnt;

	int n,p;

	while(1){
		cin>>n>>p;
		if(n==-1&&p==-1) break;
		cnt=0;
		while(1){
			if(n<prime[cnt]) break;
			cnt++;
		}
		for(int i=0;i<200000;i++) table[i]=0;
		for(int i=cnt;i<cou;i++){
			for(int j=i;j<cou;j++){
				table[prime[i]+prime[j]]++;
			}
		}
		while(p>0){
			p-=table[cnt];
			cnt++;
		}
		cout<<cnt-1<<endl;
	}
}

C++: #include <iostream>
#include <set>
#include <vector>
#include <algorithm>

using namespace std;

#define N 1000000
#define all(p) p.begin(),p.end()
bool primes[N];

int main() {
    vector<int> prime;
    
    primes[0] = primes[1] = 1;

    for (int i=2;i<N;i++) {
        if(!primes[i]) {
            for (int j=i;j<N;j+=i) primes[j] = 1;
            prime.push_back(i);
        }
        if(prime.size() == 100100) break; 
    }
    int n,p;
    while(cin >> n >> p && !(n==-1&&p==-1) ) {
        int i;
        vector<int> mp;
        for (i=0;prime[i]<n;i++);
        for (int j=i;j<i+25;j++)  for(int k=j;k<i+25;k++) 
                mp.push_back(prime[j]+prime[k]);
        sort(all(mp));
        cout << mp[p-1] << endl;
    }
    return 0;
}

C++: #include<stdio.h>
#include<vector>
#include<algorithm>
int P(int x)
{
	if(x<2)return 0;
	if(x==2)return 1;
	if(x%2==0)return 0;
	for(int i=3;i*i<=x;i+=2)if(x%i==0)return 0;
	return 1;
}
int main()
{
	int m,p,i,j,s;
	while(scanf("%d%d",&m,&p),p>0)
	{
		std::vector<int>u,v;
		for(i=m+1;s=u.size(),s<p;++i)if(P(i))u.push_back(i);
		for(i=0;i<s;++i)for(j=i;j<s;++j)v.push_back(u[i]+u[j]);
		std::sort(v.begin(),v.end());
		printf("%d\n",v[p-1]);
	}
	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <set>
#include <map>

using namespace std;

const int mx = 106001;

int func(vector<int> vec, int n, int p)
{
  int r = 0, q, l = vec.size(), t;
  map<int,int> mpp1;
  map<int, bool> mpp2;
  set<int> stt;

  for(q = 0;vec[q] <= n && q < l; q++);

  for(int i = 0; i < p && i+q < l; i++){
    for(int j = i; j < p && j+q < l; j++){
      t = vec[i+q] + vec[j+q];
      if(!mpp2[t]){
	mpp2[t] = true;
	mpp1[t] = 1;
	stt.insert(t);
      } else {
	mpp1[t]++;
      }
    }
  }
  t = 0;
  for(set<int>::iterator it = stt.begin(); it != stt.end(); it++){
    t += mpp1[(*it)];
    if(t >= p){
      r = *it;
      break;
    }
  }

  return r;
}

int main()
{
  int n, p;
  bool a[106001];
  vector<int> vec;
  fill(a, a+mx, true);
  a[0] = a[1] = false;

  for(int i = 2; i < mx; i++){
    if(a[i]){
      vec.push_back(i);
      for(int j = i+i; j < mx; j+=i){
	a[j] = false;
      }
    }
  }

  while(cin>>n>>p && (n+p) > -1){
    cout << func(vec, n, p) << endl;
  }

  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <list>
#include <cmath>
#include <fstream>
#include <algorithm>
#include <string>
#include <queue>
#include <set>
#include <map>
#include <complex>
#include <iterator>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <stack>
#include <climits>

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
double EPS=1e-10;
double EQ(double a,double b){
	return abs(a-b)<EPS;
}
bool f[200001];
void solve(){
	for(int i=0;i<=200000;i++) f[i]=1;
	f[0]=0,f[1]=0;
	for(int i=2;i*i<=200000;i++){
		if(f[i])
			for(int j=i*2;j<=200000;j+=i){
				f[j]=0;
			}
	}
	vector<int> v1,v2;
	for(int i=2;i<=200000;i++) if(f[i]) v1.push_back(i);
//for(int i=0;i<100;i++) cout<<v1[i]<<endl;
	int n,p;
	while(cin>>n>>p,n!=-1&&p!=-1){
		int idx = upper_bound(v1.begin(),v1.end(),n)-v1.begin();
//cout<<idx<<endl<<endl;;
		v2.clear();
		for(int i=0;i<200;i++){
			for(int j=i;j<200;j++) v2.push_back(v1[i+idx]+v1[j+idx]);
		}
		sort(v2.begin(),v2.end());
		cout<<v2[p-1]<<endl;
	}
}

int main(){
   solve();
}