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 <vector>
#include <algorithm>
#define REP(i,n) for(int i=0;i<(n);i++)
using namespace std;

const int MAX_N = 300000;
bool prime[MAX_N+1];

void sieve()
{
  fill(prime, prime+MAX_N+1, true);
  prime[0] = prime[1] = false;
  for(int i = 2; i <= MAX_N; i++)
    if(prime[i])
      for(int j = i*2; j <= MAX_N; j += i)
        prime[j] = false;
}

int main()
{
  sieve();
  while(1){
    int N, P;
    cin >> N >> P;
    if(N == -1 && P == -1) break;
    int n = N+1;
    int c = 0;
    int m[30];
    while(c < 30){
      if(prime[n]){
        m[c] = n;
        c++;
      }
      n++;
    }
    vector<int> v;
    REP(i,30){
      for(int j = i; j < 30; j++){
        v.push_back(m[i]+m[j]);
      }
    }
    sort(v.begin(),v.end());
    cout << v[P-1] << endl;
  }
}

C++: #include<iostream>
#include<string>
#include<cstdio>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
#include<set>
#include<complex>
#define vi vector<int>
#define vvi vector<vector<int> >
#define ll long long int
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vb vector<bool>
#define vc vector<char>
#define vs vector<string>
#define ld long double
#define INF 1e9
#define EPS 0.0000000001
#define rep(i,n) for(int i=0;i<n;i++)
#define CC puts("-------ok--------");
#define all(in) in.begin(), in.end()
#define bv vector<bool>
using namespace std;
typedef pair<int, int> PI;
#define MAX 1e8
int main(){
    int n,n2;
    vector<bool>check(MAX+1,true);
    vector<int>Primenumber(MAX+1,0); //Primearray
    int counter =0;                  //Primearray counter;
    for(int i = 2; i<MAX+1;i++){
        if(check[i]){
            for(int j = 2;i*j<MAX;j++)
                check[i*j] = false;//?´???°??????Primearray???????´??????????????????°?????¨???false???
            Primenumber[counter] = i;
            counter++;
        }
    }
    check[0]=false;
    check[1]=false;
    while(cin>>n>>n2,n+n2+2){
        vi v;
        for(int i=2*n;;i++){
            if(i<4)continue;
            //cout<<i<<endl;
            for(int j=i;(double)j>=(double)i/2;j--){
                if(check[j]&&check[i-j]&&i-j>n&&j>n)v.push_back(i);
                if(v.size()>n2)goto E;
            }
        }
    E: //ep(i,10)cout<<v[i]<<endl;
        cout<<v[n2-1]<<endl;
    }
}

C++: #include<iostream>
#include<cmath>
#include<algorithm>
using namespace std;
int s[1000], k[10000], n, m, t, p, i, j;
int main() {
	while (true) {
		t = 0; p = 0;
		cin >> n >> m;
		if (n == -1) { break; }
		while (t <= m) {
			if (n < 2) { goto E; }
			for (i = 2; i <= sqrt(n); i++) {
				if (n%i == 0) {
					goto E;
				}
			}
			s[t] = n;
			t++;
		E:;
			n++;
		}
		for (i = 0; i < m; i++) { for (j = i; j < m; j++) { k[p] = s[j] + s[i]; p++; } }
		sort(k, k + p);
		cout << k[m - 1] << endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int a[10000]={2,3},i,j,k,c=2,b[100002][101],q;
int main(){
  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+20;j++){
      for(c=j;c<j+20;c++){
        b[i][q++]=a[j]+a[c];
      }
    }
    sort(b[i],b[i]+q-1);
  }
  while(cin>>i>>j){
    if(i<0)break;
    cout<<b[i][j-1]<<endl;
  }
}

C++: #include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

#define rep(i, n) for (int i = 0; i < int(n); ++i)

const int SIZE= 1000000;
bool prime[SIZE];
vector<int> primes;

int main() {
  rep (i, SIZE) prime[i] = true;
  prime[0] = prime[1] = false;
  for (int i = 0; i * i <= SIZE; ++i) {
    if (!prime[i]) continue;
    for (int j = i * i; j <= SIZE; j += i) {
      prime[j] = false;
    }
  }
  rep (i, SIZE) if (prime[i]) primes.push_back(i);
  int n, p;
  while (true) {
    cin >> n >> p;
    if (n == -1 && p == -1) break;
    int pos = upper_bound(primes.begin(), primes.end(), n) - primes.begin();
    vector<int> res;
    rep (i, p) rep (j, p) {
      res.push_back(primes[pos + i] + primes[pos + i + j]);
    }
    sort(res.begin(), res.end());
    cout << res[p - 1] << endl;
  }
  return 0;
}