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<algorithm>
#include<vector>
using namespace std;

int main(){
  vector <int> result;
  int i,j,n,p,k,data[110000],primenum[100000];
  for(i = 0; i < 100001; i++){
    data[i]=0;
  }

  for(i = 0; i < 100000; i++){
    primenum[i]=0;
  }


  for(i = 2; i*i < 110000; i++){
    if(data[i]==0){
      for(j = 2*i; j < 110000; j+=i){
	data[j]=1;
      }
    }
  }
  data[0]=1;
  data[1]=1;
 
  while(1){
    result.clear();
    cin >> n >> p;
    if(n==-1 && p==-1)break;
    j = 0;
    for(i = n+1; i < 110000; i++){
      if(data[i]==0){
	primenum[j]=i;
	j++;
	if(j==1000)break;
      }
    }

    //for(i = 0; i < 30; i++){
    // cout <<"primenum[" << i << "]" << primenum[i] << endl;
    // }
      for(i = 0;i < 100; i++){
	for(k = i; k < 100; k++){
	result.push_back(primenum[i]+primenum[k]);
	//	cout << "primenum[i]" <<primenum[i] <<"primenum[k]" << primenum[k] << endl;
	}
      }

     
      
      sort(result.begin(),result.end());
      // for(i = 0; i < 100; i++){
      //	cout << "result[" <<i<< "]"<<result[i] << endl;
      // }
      cout << result[p-1] << endl;
      
    }
   return 0;
}

C++: #include<bits/stdc++.h>
#define INF 200000
using namespace std;

bool sosuu[INF];
int main() {
	memset(sosuu, true, sizeof(sosuu));
	sosuu[0] = sosuu[1] = false;
	for (int a = 2; a < INF; a++) {
		if (sosuu[a]) {
			for (int b = a * 2; b < INF; b+=a)sosuu[b] = false;
		}
	}
	int x, y;
	while (cin >> x >> y, (x+1)|(y+1)) {
		int s[20000];
		fill(s, s + (y+1)*(y+1), 1 << 29);
		int sum = 0, l = 0;
		for (int z = x+1; l <= y; z++) {
			if (sosuu[z]) {
				l++;
				int r = l;
				for (int i = z; r <= y; i++) {
					if (sosuu[i]) {
						r++;
						s[sum] = z + i;
						sum++;
					}
				}
			}
		}
		sort(s, s + (y + 1)*(y + 1));
		cout << s[y] << endl;
	}
}

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

int main(int argc, char *argv[])
{
    int n, p, m;
    bool flg;
    vector<int>::iterator itr;
    while (cin >> n >> p && n != -1) {
        vector<int> prime, sums;
        for (int i = n + 1;; ++i) {
            flg = true;
            if (i == 2) {
                prime.push_back(i);
            } else if (i % 2 == 0 || i < 2) {
                continue;
            } else {
                for (int j = 3; j * j <= i; j += 2) {
                    if (i % j == 0)
                        flg = false;
                }
                if (flg)
                    prime.push_back(i);
                else
                    continue;
            }
            for (itr = prime.begin(); itr != prime.end(); ++itr)
                sums.push_back(*itr + i);
            sort(sums.begin(), sums.end());
            if (sums.size() > p && sums[p] < i + prime[0]) {
                cout << sums[p - 1] << endl;
                break;
            }
        }
    }
    return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;
typedef long long ll;

int era[102000];
void initEra(){
    for(int i = 2; i < 102000; i++)era[i] = 1;
    for(int i = 2; i * i < 102000; i++){
        if(era[i] == 0)continue;
        for(int j = i + i; j < 102000; j += i)era[j] = 0;
    }
}

int main(){
    initEra();
    vector<int>prime;
    for(int i = 0; i < 102000; i++){
        if(era[i])prime.push_back(i);
    }
    
    for(int n, p; cin >> n >> p;){
        if(n < 0)break;
        vector<int>A;
        for(int i = 0; A.size() < p; i++){
            if(prime[i] > n)A.push_back(prime[i]);
        }
        vector<int>B;
        for(int i = 0; i < A.size(); i++){
            for(int j = i; j < A.size(); j++){
                B.push_back(A[i] + A[j]);
            }
        }
        sort(B.begin(), B.end());
        cout << B[p - 1] << endl;
        // for(int i = 0; i < 10; i++)cout << "#" << B[i] << endl; 
        // break;
    }

    return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <string>
#include <sstream>
#include <vector>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <utility>
 
#define INF 999999999
#define mod 1000000007
 
#define rep(i,n) for(int i=0;i<int(n);i++)
#define rrep(i,n) for(int i=(n);i>=0;i--)
#define REP(i,a,b) for(int i=(a);i<int(b);i++)
#define all(x) (x).begin(),x.end()
#define pb push_back
#define MOD(x) (x%(mod))
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef pair<int,int> pi;
 
/*---------------------------------------------------*/
int prime[13000];
bool is_prime[150000];
 
void sieve(){
  int p=0;
  rep(i,150000)is_prime[i]=true;
  is_prime[0]=is_prime[1]=false;
  REP(i,2,150000){
    if(is_prime[i]){
      prime[p++]=i;
      for(int j=2*i;j<150000;j+=i)is_prime[j]=false;
    }
  }
}
 
void solve(int n,int p){
  vector<ll> v;
  int x=0;
  while(prime[x]<=n){
    x++;
  }
   
  REP(i,x,x+p){
    REP(j,i,x+p){
      v.push_back(prime[i]+prime[j]);
    }
  }
  sort(all(v));
  cout<<v[p-1]<<endl;
}
 
int main(){
  int n,p;
  sieve();
  while(cin>>n>>p){
    if(n==-1&&p==-1)break;
    solve(n,p);
  }
  return 0;
}