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 <vector>
#include <iostream>
#include <utility>
#include <algorithm>
#include <string>
#include <deque>
#include <tuple>
#include <queue>
#include <functional>
#include <cmath>
#include <iomanip>
#include <map>
//cin.sync_with_stdio(false);
//streambuf
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
vector<char> pf(1000000, 1);
vector<int> prime;
int list[10000];
int main() {
	pf[0] = pf[1] = 0;
	for (int i = 2; i < 1000000; i++) {
		if (!pf[i])continue;
		for (int j = 2 * i; j < 1000000; j += i)pf[j] = 0;
	}
	for (int i = 2; i < 1000000; i++) {
		if (pf[i])prime.push_back(i);
	}
	int n, p;
	while (cin >> n >> p, n!=-1) {
		auto ptr = lower_bound(prime.begin(), prime.end(),n);
		int cnt = 0;
		for (int i = 0; i < p; i++) {
			for (int j = i; j < p; j++) {
				list[cnt] = ptr[i] + ptr[j];
				cnt++;
			}
		}
		sort(list, list + cnt);
		cout << list[p - 1] << endl;
	}

}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <utility>
#include <cstring>
#include <iomanip>
#include <numeric>
#include <cmath>
#include <cassert>
#include <complex>
#define repi(i, x, n) for(int i = x; i < n; i++)
#define rep(i, n) repi(i, 0, n)
#define endl "\n"
#define ing long long
using namespace std;
const int INF = 1<<30;
const int MOD = (int)1e9 + 7;
const int MAX_N = (int)1e6;
#define debug(x) cout << #x << ": " << x << endl
signed main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, P;
    vector<int> prime(MAX_N, 1);
    prime[0] = prime[1] = 0;
    for(int i = 2; i * i < MAX_N; i++)
    {
        for(int j = 2 * i; j < MAX_N; j += i) prime[j] = 0;
    }
    while(cin >> N >> P)
    {
        if(N == -1 and P == -1) break;
        vector<int> num;
        for(int i = N + 1; i < MAX_N; i++) if(prime[i]) num.push_back(i);
        vector<int> L;
        for(int i = 0; i < 100; i++)
        {
            for(int j = i; j < 100; j++) L.push_back(num[i] + num[j]);
        }
        sort(L.begin(), L.end());
        cout << L[P - 1] << endl;
    }
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int MAX = 110000;
int main(){
  vector<bool> prime(MAX + 1, true);
  prime[0] = false;
  prime[1] = false;
  for (int i = 2; i <= MAX; i++){
    if (prime[i]){
      for (int j = i * 2; j <= MAX; j += i){
        prime[j] = false;
      }
    }
  }
  while (1){
    int N, P;
    cin >> N >> P;
    if (N == -1 && P == -1){
      break;
    }
    vector<int> p;
    for (int i = N + 1; i <= MAX; i++){
      if (prime[i]){
        p.push_back(i);
        if (p.size() == P){
          break;
        }
      }
    }
    vector<int> sum;
    for (int i = 0; i < P; i++){
      for (int j = i; j < P; j++){
        sum.push_back(p[i] + p[j]);
      }
    }
    sort(sum.begin(), sum.end());
    cout << sum[P - 1] << endl;
  }
}

C++: #include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#define MAXNUM 200274

int main(void){
	int n, p, i, j, count1, count2, flag[MAXNUM + 1], tmp[MAXNUM + 1];
	for(i = 0;i <= MAXNUM;i++)
		flag[i] = 1;
	flag[0] = flag[1] = 0;
	for(i = 2;i <= sqrt((double)MAXNUM);i++){
		for(j = 2 * i;j <= MAXNUM;j += i)
			flag[j] = 0;
	}
	while(1){
		scanf("%d%d",&n,&p);
		if(n == -1 && p == -1)
			break;
		count1 = 0;
		memset(tmp,0,sizeof(tmp));
		for(i = n + 1;count1 < p;i++){
			if(flag[i]){
				count1++;
				count2 = 0;
				for(j = i;count2 < p;j++){
					if(flag[j]){
						count2++;
						tmp[i + j]++;
					}
				}
			}
		}
		count1 = 0;
		for(i = n + 1;count1 < p;i++){
			if(tmp[i])
				count1 += tmp[i];
		}
		printf("%d\n",i - 1);
	}
	return 0;
}

C++: #include <vector>
#include <iostream>
#include <algorithm>
 
using namespace std;
 
bool is_prime(int n, int k = 3)
{
    if(n < k * k) { return true; }
     
    if(n % k == 0) { return false; }
     
    return is_prime(n, k + 2);
}
 
int main()
{
    vector<int> prime = {2};
     
    for(int i = 3; i < 101300; i += 2)
    {
        if(is_prime(i))
        {
            prime.push_back(i);
        }
    }
     
    int n, m;
     
    while(true)
    {
        scanf("%d", &n);
        scanf("%d", &m);
         
        if(n == -1 && m == -1) { break; }
         
        int ptr = distance(prime.begin(), lower_bound(prime.begin(), prime.end(), n + 1));
         
        vector<int> c; int r = min(22, max(m / 2, 8)) - 1;
        
        for(int i = ptr + r; i >= ptr; i--)
        {
            for(int j = ptr + r; j >= i; j--)
            {
                c.push_back(prime[i] + prime[j]);
            }
        }
        
        sort(c.begin(), c.end());
         
        printf("%d\n", c[m - 1]);
    }
     
    return 0;
}