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 <algorithm>
#include <vector>
#include <set>
#include <math.h>
#include <map>
#include <numeric>
using namespace std;
typedef long long int ll;

const int mx=200005;

bool is_prime[mx];
vector<int> prime;

void makeprime(int n){
    is_prime[0]=is_prime[1]=1;
    for(int i=2;i<=n;i++){
        if(!is_prime[i]){
            prime.push_back(i);
            for(int j=2*i;j<=n;j+=i){
                is_prime[j]=1;
            }
        }
    }
}

int main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
    makeprime(mx);
    while(1){
        int n,p; cin >> n >> p;
        if(n==-1&&p==-1)break;
        vector<int> a;
        for(int i=n+1;i<mx;i++){
            if(!is_prime[i]){
                a.push_back(i);
            }
            if(a.size()==p)break;
        }
        vector<int> v;
        for(int i=0;i<p;i++){
            for(int j=i;j<p;j++){
                v.push_back(a[i]+a[j]);
            }
        }
        sort(v.begin(),v.end());
        printf("%d\n",v[p-1]);
    }
}

C++: #include<iostream>
#include<vector>
#include<set>
#include<algorithm>
using namespace std;

bool isPrime(int n){
	if(n<=1 || n%2==0&&n!=2)return false;
	for(int i=2;i*i<=n;i++)if(n%i==0)return false;
	return true;
}
vector<int> primes(int n){
	vector<int> res;
	while(res.size()<100){
		n++;
		if(isPrime(n))res.push_back(n);
	}
	return res;
}

struct A{
	int sum,n,i;
	A(){}
	A(int a,int b,int c):sum(a),n(b),i(c){}
	bool operator<(const A &a)const{return sum<a.sum;}
};
int main(){
	int n,p;
	while(cin>>n>>p,~n&&~p){
		multiset<A> ms;
		vector<int> v=primes(n);
		int ans=-1;
		ms.insert(A(0,0,0));
		while(1){
			A a=*ms.begin();
			ms.erase(ms.begin());
			if(a.n==2){
				if(--p==0){
					ans=a.sum;
					break;
				}
			}else{
				for(int i=a.i;i<v.size();i++){
					ms.insert(A(a.sum+v[i],a.n+1,i));
				}
			}
		}
		cout<<ans<<endl;
	}
	return 0;
}

C++: #include<bits/stdc++.h>
#define INF 200000
using namespace std;

bool sosuu[INF];
int main() {
	memset(sosuu, true, sizeof(sosuu));
	sosuu[0] = sosuu[1] = false;
	for (int a = 2; a < INF; a++) {
		if (sosuu[a]) {
			for (int b = a * 2; b < INF; b+=a)sosuu[b] = false;
		}
	}
	int x, y;
	while (cin >> x >> y, x | y) {
		int s[20000];
		fill(s, s + (y+1)*(y+1), 1 << 29);
		int sum = 0, l = 0;
		for (int z = x+1; l <= y; z++) {
			if (sosuu[z]) {
				l++;
				int r = l;
				for (int i = z; r <= y; i++) {
					if (sosuu[i]) {
						r++;
						s[sum] = z + i;
						sum++;
					}
				}
			}
		}
		sort(s, s + (y + 1)*(y + 1));
		cout << s[y] << endl;
	}
}

C++: #include<iostream>
#include<string>
using namespace std;
long long m[100],c[10000],prime[200];
int main(){
	long long n,p;
	int count=0,i=2;
	while(true){
		bool t=true;
		for(int j=2;j*j<=i;j++){
			if(i%j==0)
				t=false;
		}
		if(t==true){
			prime[count]=i;
			count++;
		}
		if(count==200)
			break;
		i++;
	}
	while(true){
		cin>>n>>p;
		if(n==-1&&p==-1)
			break;
		for(int i=0;i<p*p;i++){
			c[i]=1000000;
		}
		if(n==0)
			n++;
		int i=n+1,count=0;
		while(true){
			bool t=true;
			for(int j=0;j<200;j++){
				if(i!=prime[j]&&i%prime[j]==0)
					t=false;
			}
			if(t==true){
				m[count]=i;
				count++;
			}
			if(count==p)
				break;
			i++;
		}
		for(int i=0;i<p;i++){
			for(int j=0;j<=i;j++){
				c[i*p+j]=m[i]+m[j];
			}
		}
		for(int i=0;i<p*p-1;i++){
			for(int j=p*p-1;j>i;j--){
				if(c[j]<c[j-1]){
					int tmp=c[j];
					c[j]=c[j-1];
					c[j-1]=tmp;
				}
			}
		}
		cout<<c[p-1]<<endl;
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<string>
#include<algorithm>
using namespace std;
int main(){
  int n,p;
  while(cin >> n >> p){
    if(n==-1)break;
    int m,sosu[200]={},count=0,judge=1;
    for(m=n+1;count<=200;m++){
      for(int i=2;i<m;i++){
        if(m%i==0){
          judge=0;
        }
      }
      if(judge==1&&m!=1){
        sosu[count]=m;
        count++;
      }
      else judge=1;
    }
    vector<int> sum(200);
    int COUNT=0;
    for(int i=0;i<10;i++){
      for(int j=i;j<25;j++){
        sum[COUNT]=sosu[i]+sosu[j];
        COUNT++;
      if(COUNT==200)break;
      }
      if(COUNT==200)break;
    }
    sort(sum.begin(),sum.end());
    cout << sum[p-1] << endl;
  }
}

C++: #include <iostream>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <string>
#include <sstream>
#include <numeric>
#define rep(i, j) for(int i = 0; i < j; i++)
#define all(i) i.begin(), i.end()
using namespace std;
vector<bool> era(1000010, true);
void makePrimeTable(int n)
{
	era[0] = false; era[1] = false;
	for (int i = 2; i <= n; i++)
	{
		if (era[i]) { for (int j = i * 2; j <= n; j += i) { era[j] = 0; } }
	}
}
int main()
{
	makePrimeTable(200000);
	int N, P; while (cin >> N >> P && N != -1)
	{
		vector<int> dat(0);
		vector<int> prm(0);
		if (P > 100) { P = P / 10; }
		while (1)
		{
			N++;
			if (era[N]) { prm.push_back(N);}
			if (prm.size() == P) { break; }
		}
		for (int i = 0; i < P; i++) for (int j = i; j < P; j++) { dat.push_back(prm[i] + prm[j]); }
		sort(all(dat)); 
		printf("%d\n", dat[P - 1]);
	}
	return 0;
}