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;

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = long long;
using P = std::tuple<int,int>;

const int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1}, dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};

vector<int> primes;
bool isNotPrime[200100];

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    primes.emplace_back(2);
    for(int i=4;i<=200000;i+=2){
        isNotPrime[i] = true;
    }

    for(int i=3;i<=200000;i+=2){
        if(isNotPrime[i]){continue;}

        primes.emplace_back(i);

        for(int j=2*i;j<=200000;j+=i){
            isNotPrime[j] = true;
        }
    }

    while(true){
        int n, p;
        std::cin >> n >> p;
        if(n == -1){break;}

        vector<int> v;
        auto it = upper_bound(primes.begin(), primes.end(), n);
        // std::cout << "*it: " << *it << std::endl;
        for(int i=0;i<100;++i){
            for(int j=i;j<100;++j){
                v.emplace_back(*(it+i) + *(it+j));
            }
        }

        sort(v.begin(), v.end());

        // for(int i : v){
        //     std::cout << i << std::endl;
        // }
        // std::cout << "----------" << std::endl;
        
        std::cout << v[p-1] << std::endl;
    }
}

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[10000] = {0};
		if(isprime(n)) prime_array[0] = n;
		else prime_array[0] = min_prime(n);
		for(int i = 0; i < 50; i++){
			prime_array[i + 1] = min_prime(prime_array[i]);
		}
		int k = 0;
		for(int i = 0; i < p; i++){
			for(int j = i; j < p; 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)
{
	int i = 1;
	while(1){
		if(isprime(n + i)) return n + i;
		else i++;
	}
}

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<algorithm>
#include<iostream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#define N 50
using namespace std;
int main(){
  int i,j,k,l;
  int a[10000][N+1],b[(N+1)*N/2],n,p;
  a[0][0]=2;
  j=1;
  for(i=3;j<10000;i+=2){
    l=(int)sqrt(i)+1;
    for(k=3;k<l;k+=2){
      if(i%k==0)
	break;
    }
    if(k>=l){
      a[j][0]=i;
      j++;
    }
  }
  for(i=0;i<10000-N;i++){
    for(j=0;j<N;j++){
      a[i][j+1]=a[i][0]+a[i+j][0];
    }
  }
  while(cin>>n>>p&&(n!=-1||p!=-1)){
    for(i=0;a[i][0]<=n;i++);
    l=0;
    for(j=0;j<N;j++){
      for(k=0;k<N-j;k++){
	b[l]=a[i+j][k+1];
	l++;
      }
    }
    sort(b,b+(N+1)*N/2);
    cout<<b[p-1]<<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>

#define CH(N,A,B) (A<=N&&N<B)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define RREP(i,a,b) for(int i=(b-1);a<=i;i--)

using namespace std;

int N, P;
bool flag[102000];
vector<int> v;

int main() {
  REP(i,0,102000) flag[i] = true;
  for(int i = 2; i<102000; i++){
    if(!flag[i]) continue;
    v.push_back(i);
    for(int j = i*2; j<102000; j += i){
      flag[j] = false;
    }
  }

  while(1){
    cin>>N>>P;
    if(N==-1&&P==-1) break;
    int pos;
    REP(i,0,v.size()){
      if(N < v[i]){
        pos = i;
        break;
      }
    }
    vector<int> tv, nums;
    int cnt = 0;
    REP(i,pos,v.size()){
      if(cnt>=1000) break;
      tv.push_back(v[i]);
      REP(j,0,tv.size()){
        cnt++;
        nums.push_back(v[i]+tv[j]);
      }
    }
    sort(nums.begin(),nums.end());
    cout<<nums[P-1]<<endl;
  }

  return 0;
}