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;

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define ALL(a) (a).begin(),(a).end()
const int INF = INT_MAX/3;
const double EPS = 1e-14;

template<typename U, typename T>
void chmin(U &x, T y) { x = min(x, y); }

template<typename U, typename T>
void chmax(U &x, T y) { x = max(x, y); }

typedef long long int lli;

int N, P;

const int PRIMEMAX = 150000;
int FACTOR[PRIMEMAX];
vector<int> Primes;
void sieve(lli upb) {
  FACTOR[0] = FACTOR[1] = -1;
  for(lli n = 0; n < upb; ++n) {
    if (FACTOR[n] != 0) continue;
    Primes.push_back(n);
    lli kn = n * n;
    while (kn < PRIMEMAX) { FACTOR[kn] = n; kn += n; }
  }
}

bool is_prime(int n) {
  return FACTOR[n] == 0;
}

int main() {
  cout << fixed << setprecision(12);
  sieve(PRIMEMAX);
  while (cin >> N >> P and N != -1) {
    auto iter = upper_bound(ALL(Primes), N);
    vector<int> v;
    REP(i, 100) FOR(j, i, 100 + i) {
      v.push_back(*(iter + i) + *(iter + j));
    }
    sort(ALL(v));
    cout << v[P-1] << endl;
  }
  return 0;
}

C++: // AOJ 2150

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

bool prime[1000000];
void makeprime()
{
	fill(prime, prime + 1000000, true);
	prime[0] = prime[1] = false;
	for (int i = 4; i < 1000000; i+=2) prime[i] = false;
	for (int i = 3; i*i < 1000000; i += 2){
		if (prime[i]){
			for (int j = i*2; j < 1000000; j += i){
				prime[j] = false;
			}
		}
	}

	return;
}

int main(void)
{
	int n, p;
	makeprime();
	while (cin >> n >> p, (n != -1 && p != -1)){
		vector <int> primenum;
		for (int i = n+1; i < n + p + 500; i++){
			if (prime[i]){
				primenum.push_back(i);
			}
		}

		vector <int> ret;
		for (int i = 0; i < (int)primenum.size(); i++){
			for (int j = i; j < (int)primenum.size(); j++){
				ret.push_back(primenum[i] + primenum[j]);
			}
		}

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

		cout << ret[p-1] << endl;
	}

	return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>
#include <fstream>
#include <bitset>
#include <time.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef complex<double> Point;

#define PI acos(-1.0)
#define EPS 1e-10
const ll INF = (1LL << 31) - 1;
const ll MOD = 1e9 + 7;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,N) for(int i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define EQ(a,b) (abs((a)-(b))<EPS)
#define EQV(a,b) ( EQ((a).real(), (b).real()) && EQ((a).imag(), (b).imag()) )
#define fi first
#define se second
#define N_SIZE (1LL << 20)
#define NIL -1
#define MAX_N 100100 * 3

bool is_prime[200100];
int prime[200100];

void sieve(int n) {
	int p = 0;
	fill(is_prime, is_prime + 200100, 1);
	is_prime[0] = 0;
	is_prime[1] = 0;
	for (int i = 2; i < n; i++) {
		if (is_prime[i] == 1) {
			prime[p] = i;
			p++;
			for (int j = 2 * i; j < n; j += i) {
				is_prime[j] = 0;
			}
		}
	}
}

ll n, p;

int main() {
	sieve(200000);
	while (cin >> n >> p&&n + p != -2) {
		ll now = 0;
		REP(i, 200100) {
			if (prime[i] > n) {
				now = i;
				break;
			}
		}
		vector<ll> vp;
		//cout << now << " " << now + p << endl;
		FOR(i, now, now + p + 1) {
			FOR(j, i, now + p + 1) {
				vp.push_back(prime[i] + prime[j]);
			}
		}
		sort(ALL(vp));
		//REP(i, vp.size()) {
		//	cout << vp[i] << endl;
		//}
		cout << vp[p - 1] << endl;
	}
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>
#include <fstream>

using namespace std;

#define FOR(i,a,b) for(long long i=(a);i<(b);i++)
#define REP(i,N) for(long long i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define fi first
#define se second

#define PI acos(-1.0)
#define INF 10e15+9
#define EPS 1e-10
#define MAX_N 100100
#define MAX_M 100100

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<double, double> PD;
typedef pair<string, ll> PS;
typedef vector<ll> V;
typedef pair<P, char> PC;

int n, p;

bool is_prime[1000000];
int prime[1000000];
int field[10000][10000];

int main(){
	fill(is_prime, is_prime + 1000000, 1);
	is_prime[0] = 0;
	is_prime[1] = 0;
	int po = 0;
	for (int i = 0; i <= 101000; i++){
		if (is_prime[i]){
			prime[po++] = i;
			for (int j = 0; j <= 101000; j += i){
				is_prime[j] = 0;
			}
		}
	}
	while (cin >> n >> p&&n != -1 && p != -1){
		int ans = 0;
		REP(i, po){
			REP(j, po){
				
			}
		}
		cout << ans << endl;
	}
}