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;
 
using ll=long long;
#define int ll
 
#define FOR(i,a,b) for(int i=int(a);i<int(b);i++)
#define REP(i,b) FOR(i,0,b)
 
int read(){
    int i;
    scanf("%lld",&i);
    return i;
}
 
bool is_prime(int n){
    if(n==0||n==1) return false;
    if(n==2) return true;
    for(int i=2;i<n;i++){
        if(n%i==0) return false;
    }
    return true;
}
 
signed main(){
    while(true){
        int N=read(),P=read();
        if(N==-1&&P==-1) break;
        vector<int> prime;
        vector<int> matsuzaki;
        while(1){
            if(is_prime(N)){
                prime.push_back(N);
                REP(j,prime.size()){
                    matsuzaki.push_back(prime[j]+N);
                }
                sort(matsuzaki.begin(),matsuzaki.end());
                if(prime.size()>=P+10){
                    //REP(i,prime.size()) cout << prime[i] << endl;
                    cout << matsuzaki[P-1] << endl;
                    break;
                }
            }
            N++;
        }
    }
     
}

C++: #include <bits/stdc++.h>
using namespace std;
#define lp(i,n) for(int i=0;i<n;i++)
int memo[110000];
vector<int> st;
vector<int> so;

void calc(int now,int endp){
	for(int i=now;i<=endp;i++){
		st.push_back(so[now]+so[i]);
	}
	return;
}

int main(){
	for(int i=2;i<100;i++){
		if(memo[i]==0){
			so.push_back(i);
			memo[i]=1;
			int s=i;
			for(int j=i;j<100;j=j+s){
				memo[j]=1;
			}
		}
	} 
	while(1){
		int n,p;
		cin>>n>>p;
		if(n==-1&&p==-1) break;
		st.clear();
		int sp,i=0;
		while(1){
			if(so[i]>n){
				sp=i;
				break;
			}
			i++;
		}
		int endp=sp+p+p;
		for(int i=sp;i<endp;i++){
			calc(i,endp);
		}
		sort(st.begin(),st.end());
		cout<<st.size()<<endl;
		cout<<st[p-1]<<endl;
	}
	return 0;
}

C++: #include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;
const int MAX_P = 100;

const int MAX_PNUM = MAX_N + MAX_P * 10;

/* typedef */

typedef vector<int> vi;

/* global variables */

bool primes[MAX_PNUM + 1];
vi pnums;

/* subroutines */

int calc_prime(int max_p) {
  memset(primes, true, sizeof(primes));
  primes[0] = primes[1] = false;

  for (int p = 2; p * p <= max_p; p++)
    if (primes[p])
      for (int q = p * p; q <= max_p; q += p) primes[q] = false;

  for (int p = 2; p <= max_p; p++)
    if (primes[p]) pnums.push_back(p);

  return pnums.size();
}

/* main */

int main() {
  calc_prime(MAX_PNUM);
  
  for (;;) {
    int n, p;
    cin >> n >> p;
    if (n < 0) break;

    vi::iterator pbgn = upper_bound(pnums.begin(), pnums.end(), n);
    vi::iterator pend = min(pbgn + 2 * p, pnums.end());
    
    vi sums;
    for (vi::iterator pit0 = pbgn; pit0 != pend; pit0++)
      for (vi::iterator pit1 = pit0; pit1 != pend; pit1++)
	sums.push_back(*pit0 + *pit1);
    sort(sums.begin(), sums.end());

    cout << sums[p - 1] << endl;
  }
  
  return 0;
}

C++: #include <cstdio>
#include <iostream>
#include <cmath>
#include <ctype.h>
#include <string> 
#include <sstream>
#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <map>
#include <queue>
#include <utility>
#include <vector>

using namespace std;

int min_prime(int n);
int isprime(int n);

int main()
{
	int n, p;
	while(1){
		cin >> n >> p;
		if(n == -1 && p == -1) break;
		int prime_array[1000] = {0}, sum_array[50000] = {0};
		if(isprime(n)) prime_array[0] = n;
		else prime_array[0] = min_prime(n);
		for(int i = 0; i < (2 * p); i++){
			prime_array[i + 1] = min_prime(prime_array[i]);
		}
		int k = 0;
		for(int i = 0; i < (2 * p) + 1; i++){
			for(int j = i; j < (2 * p) + 1; j++){
				sum_array[k] = prime_array[i] + prime_array[j];
				k++;
			}
		}
		sort(sum_array, sum_array+k);
		cout << sum_array[p - 1] << endl;
	}
	return 0;
}

int min_prime(int n)
{
	while(++n){
		if(isprime(n)) break;
	}
	return n;
}

int isprime(int n)
{
	int ans;
	if(n == 0 || n == 1) ans = 0;
	else if(n == 2) ans = 1;
	else {
		for(int i = 2; i < n; i++){
			if(i * i > n) ans = 1;
			else if(n % i == 0){
				ans = 0;
				break;
			}
		}
	}
	return ans;
}

C++: #include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<vector>
using namespace std;
int main(){
  const int NUM = 200000;
  bool prime[NUM];
  prime[0] = false;
  prime[1] = false;
  for(int i=2;i<NUM;i++)
    prime[i] = true;
  for(int i=2;i*i<NUM;i++)
    for(int k=2;i*k<NUM;k++)
      prime[i*k]=false;

  int n,p,pn;
  while(true){
    cin >> n >> p;
    if (n==-1)
      break;
    int sum[p*p];
    for(int i=0;i<p*p;i++)
      sum[i] = 0;
    pn = n+1;
    for(int i=0;i<p;i++){
      while(!prime[pn])
	pn++;
      for(int j=0;j<p;j++){
	sum[j*p+i] += pn;
	sum[i*p+j] += pn;
      }
      pn++;
    }
    for(int i = 0;i<p*p;i++){
      if(i/p>i%p)
	sum[i] = 1000000;
    }
    
    sort(sum,sum+p*p);
    cout << sum[p-1] << endl;
  }
  return 0;
}