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++: // 2150.cpp
//
#include <bits/stdc++.h>
using namespace std;
const int MAX_N=100000;
const int MAX_P=100;
bool prime[MAX_N+1];
void sieve(){
  fill(prime,prime+MAX_N+1,1);

  prime[0]=prime[1]=0;
  for(int i=2;i<MAX_N;++i)
    if(prime[i])
      for(int j=i*2;j<MAX_N;j+=i)
        prime[j]=0;
}
int M(int n, int p){
  vector<int> v;
  int cnt=0;
  for(int i=n+1;cnt<100;++i){
    if(prime[i]){
      v.push_back(i);
      cnt++;
    }
  }

  vector<int> w;
  for(int i=0;i<MAX_P;++i)
    for(int j=i;j<MAX_P;++j)
      w.push_back(v[i]+v[j]);

  sort(w.begin(),w.end());
  return w[p-1];

}
int main() {
  sieve();

  int n,p;
  while(cin>>n>>p){
    if(n==-1&&p==-1) break;
    cout<<M(n,p)<<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>

#define CH(N,A,B) (A<=N&&N<B)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define RREP(i,a,b) for(int i=(b-1);a<=i;i--)

using namespace std;

int N, P;
bool flag[102000];
vector<int> v;

int main() {
  REP(i,0,102000) flag[i] = true;
  for(int i = 2; i<102000; i++){
    if(!flag[i]) continue;
    v.push_back(i);
    for(int j = i*2; j<102000; j += i){
      flag[j] = false;
    }
  }

  while(1){
    cin>>N>>P;
    if(N==-1&&P==-1) break;
    int pos;
    REP(i,0,v.size()){
      if(N < v[i]){
        pos = i;
        break;
      }
    }
    vector<int> tv, nums;
    int cnt = 0;
    REP(i,pos,v.size()){
      if(cnt==100) break;
      tv.push_back(v[i]);
      cnt++;
      REP(j,0,tv.size()){
        nums.push_back(v[i]+tv[j]);
      }
    }
    sort(nums.begin(),nums.end());
    cout<<nums[P-1]<<endl;
  }

  return 0;
}

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

using namespace std;

int main(void)
{
	int n,p;
	int check;

	int i1,i2;

	while(1){
		cin >> n >> p;
		if(n==-1 && p==-1) break;

		vector<int> sosu;

		i1=n+1;
		if(i1==1 || i1==2) {
			sosu.push_back(2);
			i1=3;
		}

		while(sosu.size()<=p){
			
			check=0;

			
			for(i2=2;i2*i2<=i1;i2++){
				if(i1%i2==0){
					check=1;
					break;
				}
			}

			if(check==0) sosu.push_back(i1);
			i1++;

		}

		vector<int> matsuzaki;

		for(i1=0;i1<sosu.size();i1++){
			for(i2=i1;i2<sosu.size();i2++){
				matsuzaki.push_back(sosu[i1]+sosu[i2]);
			}
		}

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

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

	}
	return 0;


}

C++: #define _CRT_SECURE_NO_WARNINGS // #pragma warning(disable:4996)
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <string>
#include <queue>
#include <functional>
#include <sstream>
#include <cmath>
#include <set>
#include <map>
#include <stack>
using namespace std; 

#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(a);i>=(b);i--)
#define pb push_back
#define mp(a,b) make_pair(a,b)
#define all(a) a.begin(),a.end()
#define len(x) ((int)(x).size())
#define tmax(a,b,c) max((a),max((b),(c)))
#define tmin(a,b,c) min((a),min((b),(c)))
#define debug(x) cerr << #x << " is " << x << endl;

typedef pair<int, int> Pii;
typedef map<int, int> Mii;
typedef vector<int> Vi;
typedef long long ll;
const int inf = 2e9;
const ll ll_inf = 1e17;
const int mod = 1e9 + 7;
const long double eps = 1e-10;

int e[250100];
Vi g;

int main()
{
	rep(i,2,501) {
		int j = i+i;
		while(j < 250000) {
			e[j]++;
			j += i;
		}
	}
	rep(i,2,202020) if (!e[i]) g.pb(i);
	
	while (1) {
		int n, p;
		cin >> n >> p;
		if (n==-1 && p==-1) break;
		Vi l;
		auto it = upper_bound(all(g), n)-g.begin();
		//debug(g[it]);
		rep(i,it,it+p) rep(j,i,it+p+1) {
			l.pb( g[i]+g[j] );
			//cout << g[i] << " " << g[j] << endl;
		}
		sort(all(l));
		//for (auto x: l) cout << x << " "; cout << endl;
		cout << l[p-1] << endl;
	}
	
	return 0;
}

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; break; }
            else if(n % i == 0){
                ans = 0;
                break;
            }
        }
    }
    return ans;
}