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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vector>
#include <algorithm>
#include <string>
#include <stack>
#include <queue>

#define SIZE 201000

using namespace std;


int main(){
	vector <int> table(SIZE, 1), prime;
	int k = 0;
	for(int i = 2; i < SIZE; i++){
		if(table[i] == 0)
			continue;
		prime.push_back(i);
		k++;
		for(int j = 2; i * j < SIZE; j++){
			table[i * j] = 0;
		}
	}
	
	
	
	
	while(1){
		int N, P;
		
		cin >> N >> P;
		if(N == -1 && P == -1)
			break;
		
		int under;
		for(under = 0; under < k; under++){
			if(prime[under] > N)
				break;
		}
		
		vector <int> ans;
		
		for(int i = under; i < under + 100; i++)
			for(int j = i; j < under + 100; j++)
				ans.push_back(prime[i] + prime[j]);
		
		
		sort(ans.begin(), ans.end());
		
		cout << ans[P - 1] << endl;
	}
	
	return 0;
}

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

bool isnp[200010];

int main(){
	for(int i = 2; i < 1000; ++i){
		if(!isnp[i]){
			for(int j = i * i; j <= 200000; j += i){
				isnp[j] = true;
			}
		}
	}
	
	vector<int> pr;
	for(int i = 2; i <= 200000; ++i){
		if(!isnp[i]){ pr.push_back(i); }
	}

	int n, p;
	while(scanf("%d%d", &n, &p), n != -1){
		vector<int> tbl;
		int k = upper_bound(pr.begin(), pr.end(), n) - pr.begin();
		for(int i = k; i <= k + p; ++i)
		for(int j = i; j <= k + p; ++j){
			tbl.push_back(pr[i] + pr[j]);
		}
		sort(tbl.begin(), tbl.end());
		printf("%d\n", tbl[p - 1]);
	}
}

C++: #include <cstdio>
#include <utility>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#define REP(i,n) for(int i=0;i<n;i++)
typedef long long ll;
using namespace std;
typedef vector<ll> vl;
typedef pair<ll,ll> pll;
typedef vector<pll> vpll;
typedef vector<string> vs;


int main() 
{
	ll a[10452]={};	//素数を格納する
	ll t(0);		//t番目の素数を求めたい
	while(t<10452)
	{
		if(t==0){a[t]=2;}	//最初の素数は2
		else
		{
			for(ll i =a[t-1]+1;i<110000;i++)	//前の素数+1から探索
			{
				for(ll j=0;j<t;j++)
				{
					if(i%a[j]==0){break;}	//t-1番目以前の素数で割り切れたらダメ
					if(j==(t-1)){a[t]=i;}	//t-1番目までの全てで割り切れなければ素数
				}
				if(a[t]!=0){break;}	
			}
		}
		t++;
	}
	
	ll n,p;
	while(cin >> n >> p && n!=-1 && p!=-1)
	{	
		//nより大きい最初の素数の番号を突き止める
		ll x(0);
		REP(i,n+1000){	if(a[i]>n){ x=i;	break;	}}
		
		ll b[10000]={};
		ll c(0);
		
		for(ll i=x;i<x+100;i++){
			for(ll j=i;j<x+100;j++){
				b[c]=a[i]+a[j];
				c++;
		}}
		
		sort(b,b+(50*101));
		
		cout << b[p-1] << endl;
	}
	return 0 ;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define REP(i, n) for (int i = 0; i < n; i++)
#define REPR(i, n) for (int i = n; i >= 0; i--)
#define SORT(v) sort((v).begin(), (v).end())
#define ALL(v) (v).begin(), (v).end()

vector<int> prime;
vector<int> ls;

void sieve(int N){
    prime.resize(N+1,1);
    prime[0] = prime[1] = 0;
    for(int i=2;i*i<=N;i++){
        for(int j=i*i;j<=N;j+=i){
            prime[j] = 0;
        }
    }
    for(int i=2;i<=N;i++){
        if(prime[i])ls.push_back(i);
    }
}

int main() {
    sieve(int(1e6));
    int n, p;
    vector<int> v;
    while(cin >> n >> p, n>=0){
        int k = upper_bound(ALL(ls),n)-ls.begin();
        v.clear();
        for(int i=0;i<=200;i++){
            for(int j=i;j<=200;j++){
                v.push_back(ls[i+k]+ls[j+k]);
            }
        }
        SORT(v);
        cout << v[p-1] << endl;
    }
    return 0;
}

C++: #include<iostream>
#include<string>
#include<cmath>
#include<queue>
#include<vector>
#include<functional>
#include<algorithm>
using namespace std;
bool a[200000];
int main() {
	fill(a, a + 200000, true);
	a[0] = false; a[1] = false;
	for (int i = 0; i < 200000; i++) {
		if (a[i]) {
			int j = 2;
			while (i*j < 200000) {
				a[i*j] = false;
				j++;
			}
		}
	}
	int n, p;
	while (cin >> n >> p&&n != -1 && p != -1) {
		int sum = 0;
		int b[1000];
		for (int i = n; i < 200000 && sum <= p; i++) {
			if (a[i]) {
				b[sum] = i;
				sum++;
			}
		}
		int c[10000];
		int sum2 = 0;
		for (int i = 0; i < sum; i++) {
			for (int j = i; j < sum; j++) {
				c[sum2] = b[i] + b[j];
				sum2++;
			}
		}
		sort(c, c + sum2);
		cout << c[p - 1] << endl;
	}
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
#define MAX 200000
bool isP[MAX];
vector<int> primes;
void make_table(){
  for(int i=0;i<MAX;i++)isP[i]=true;
  isP[0]=isP[1]=false;
  for(int i=2;i*i<MAX;i++){
    if(!isP[i])continue;
    for(int j=i*i;j<MAX;j+=i)isP[j]=false;
  }
  for(int i=0;i<MAX;i++)
    if(isP[i])primes.push_back(i);
}

int N,P;
int main(){
  make_table();
  vector<int> :: iterator it;
  while(1){
    cin>>N>>P;
    if(N==-1&&P==-1)break;
    it=upper_bound(primes.begin(),primes.end(),N);
    //cout<<*it<<endl;
    vector<int> t,u;
    for(int i=0;i<100;i++,it++){
      t.push_back(*it);
      for(int j=0;j<=i;j++)u.push_back(t[j]+t[i]);
    }
    sort(u.begin(),u.end());
    cout<<u[P-1]<<endl;
  }
  return 0;
}