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 <cmath>
#include <vector>
#include <algorithm>
using namespace std;

bool prime(int x)
{
	bool flag = true;

	if (x <= 1) {
		flag = false;
	}
	else if (x % 2 == 0 && x != 2) {
		flag = false;
	}
	else {
		for (int i = 3; i <= sqrt(x); i += 2) {
			if (x%i == 0) {
				flag = false;
			}
		}
	}

	return flag;
}

int M(int N, int P)
{
	vector<int> primes;

	int count = 0;
	int num = N + 1;
	while (count <= 100) {
		if (prime(num) == true) {
			primes.push_back(num);
			count++;
		}

		num++;
	}

	vector<int> answers;
	
	for (int i = 0; i <= 100; i++) {
		for (int j = i; j <= 100; j++) {
			answers.push_back(primes[i] + primes[j]);
		}
	}

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

	return answers[P - 1];
}

int main()
{
	while (true) {
		int N, P;
		cin >> N >> P;

		if(N == -1 && P == -1) {
			break;
		}

		cout << M(N, P) << endl;
	}
}

C++: #include <iostream>
#include <utility>
#include <vector>
#include <algorithm>
using namespace std;
int N,P;
int ans[10000];
int prime[1000000];
int prime_set[101];
void calc_prime(){
    prime[0] = 1;
    prime[1] = 1;
    for(int i=2;i<1000;i++){
        if(prime[i] == 0){
            for (int j=i*i;j<1000000;j+=i){
                prime[j] = 1;
            }

        }
    }

}


int main(){

    calc_prime();
    
    while(1){
        cin >>N >>P;

        if (N==-1&&P==-1)break;
        int cnt = 0;
        int i=N+1;
        while(cnt < P){
            if(prime[i] == 0){
                prime_set[cnt] = i;
                cnt++;

            }
            i++;
        }
        
        cnt=0;
        for(int i=0;i<P;i++){
            for(int j=i;j<P;j++){
                ans[cnt]=prime_set[i]+prime_set[j];
                cnt++;
            }
        }


        
        sort(ans,ans+cnt);
        //cout << prime_set[100] <<endl;
        cout << ans[P-1] <<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[50000] = {0};
        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 = 0;
    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<vector>
#include<algorithm>

#define	pb	push_back

using namespace std;

typedef	vector<int>	vi;

int main(){
	static bool era[110000];
	for(int i=2;i<340;i++){
		if(!era[i])	for(int j=i*i;j<110000;j+=i)	era[j]=true;
	}

	vi pr;
	for(int i=2;i<110000;i++)	if(!era[i])	pr.pb(i);

	for(int n,p;scanf("%d%d",&n,&p),~n;){
		vi::iterator it=upper_bound(pr.begin(),pr.end(),n);
		vi candi;
		for(int i=0;i<p;i++)for(int j=i;j<p;j++)	candi.pb(*(it+i)+*(it+j));
		sort(candi.begin(),candi.end());
		printf("%d\n",candi[p-1]);
	}

	return 0;
}

C++: #include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
#include <cstring>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define CLR(mat) memset(mat, 0, sizeof(mat))
typedef long long ll;
const ll MAX = 1000000;
bool isPrime[MAX];
vector<ll> prime;
void makePrime(){
  for (ll i = 0; i < MAX; i++){
    isPrime[i] = true;
  }
  for (ll i = 2; i * i < MAX + 1; i++){
    if(isPrime[i]){
      for (ll j = 2 * i; j < MAX; j += i) {
        isPrime[j] = false;
      }
    }
  }
  FOR(i,2,MAX) if(isPrime[i]) prime.push_back(i);
  return;
}
int main()
{
  makePrime();
  int N, R;
  while(cin >> N >> R, N != -1) {
    int j = upper_bound(prime.begin(), prime.end(), N) - prime.begin();
    vector<int> v;
    FOR(i,j,j+200) {
      FOR(k,i,j+200) {
        v.push_back(prime[i]+prime[k]);
      }
    }
    sort(v.begin(), v.end());
    cout << v[R-1] << endl;
  }
  return 0;
}