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;

const int MAX_N = 200110;

long long int prime[MAX_N]; // i番目の素数
int num_prime[MAX_N + 1];   // 何番目の素数か

// n以下の素数の数を返す
long long int sieve(long long int n) {
    long long int p = 0;
    for (long long int i = 0; i <= n; i++)
        num_prime[i] = i;
    num_prime[0] = -1;
    num_prime[1] = -1;
    for (long long int i = 2; i <= n; i++) {
        if (num_prime[i] >= 0) {
            num_prime[i] = p;
            prime[p++] = i;
            for (long long int j = 2 * i; j <= n; j += i)
                num_prime[j] = -1;
        }
    }
    return p;
}

int main(){
    int n, p;
    sieve(MAX_N);
    while(cin >> n >> p, n != -1){
        vector<long long int> v;
        int idx = n + 1;
        while(num_prime[idx] < 0)idx++;
        for(int i=num_prime[idx];i<=num_prime[idx]+p;++i){
            if(prime[i] == 0)break;
            v.push_back(prime[i]);
        }
        vector<long long int> sum;
        for(int i=0;i<v.size();++i){
            for(int j=i;j<v.size();++j){
                sum.push_back(v[i]+v[j]);
            }
        }
        sort(sum.begin(), sum.end());
        cout << sum[p-1] << endl;
    }

    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;
        
        if(m > 50) { m /= 2; }
         
        for(int i = ptr; i < ptr + m; i++)
        {
            for(int j = i; j < ptr + m; j++)
            {
                c.push_back(prime[i] + prime[j]);
            }
        }
         
        sort(c.begin(), c.end());
         
        printf("%d\n", c[m - 1]);
    }
     
    return 0;
}

C++: #define _USE_MATH_DEFINES
#include "bits/stdc++.h"
#define EPS 1e-10
using namespace std;
typedef long long llong;
#define N 105000
int main() {
	vector<bool>f(N, true);
	f[0] = false;
	f[1] = false;
	vector<int>prime;
	for (int i = 2; i <= sqrt(N); i++) {
		if (f[i]) {
			for (int j = 2; i*j < N; j++) {
				f[i*j] = false;
			}
		}
	}
	for (int i = 0; i < N; i++) {
		if (f[i]) {
			prime.push_back(i);
		}
	}

	int n, p;
	while (cin >> n >> p, p != -1) {
		auto it = upper_bound(prime.begin(), prime.end(), n);
		vector<int>ans(10000,100000000);

		for (int cnt = 0, i = 0; i < 100; i++) {
			for (int j = i; j < 100; j++) {
				ans[cnt++] = *(it + i) + *(it + j);
			}
		}
		sort(ans.begin(), ans.end());

		cout << ans[p - 1] << endl;


	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int main(){
  int a[100000]={2,3},i,j,k,c=2,b[100002][200],q;
  for(i=4;i<150000;i++){
    for(k=1,j=2;j*j<=i;j++){
      if(i%j==0){k=0;break;}
    }
    if(k)a[c++]=i;
  }k=0;
  for(i=0;i<=100000;i++){
    if(i>a[k])k++;
    for(q=0,j=k;j<k+13;j++){
      for(c=k;c<k+13;c++){
        b[i][q++]=a[j]+a[c];
      }
    }
    sort(b[i],b[i]+169);
  }
  while(cin>>i>>j,i||j)cout<<b[i][j]<<endl;
}

C++: #include <iostream>
#include <cstdlib>
#include <string>
#include <cmath>
#include <algorithm>
using namespace std;
#define N 100000

int main(){
        int n, p, sosuu[100],count=0,sum[10000];
        string keymoji;

        cin >> n >> p;
        while(n != -1 && p != -1){
                int i=n;
                count = 0;
                if(i<2)i=2;
                for(; count<p; i++){
                        int tmp;
                        if(i==2){
                                sosuu[count]=i;
                                count++;
                                continue;
                        }
                        for(int j=2;j<i;j++){
                                if((tmp=i%j) == 0)break;
                        }
                        if(tmp != 0){
                                sosuu[count]=i;
                                count++; 
                        }
                        
                }
                count =0;
                for(i=0; i<p; i++){
                        for(int j=i; j<p; j++){
                                sum[count]=sosuu[i]+sosuu[j];
                                count++;
                        }
                }

                sort(sum, sum+count);
                cout << sum[p-1] << endl;
                cin >> n >> p;

        }


}