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;

vector<int> eratosu(1000100, 1);

int solve(long N, int P) {
    vector<long> keep;
    int k;
    vector<int> sosu;
    int count = 0;
    for (int i = N + 1; count < P; i++) {
        if (eratosu[i] == 1) {
            sosu.push_back(i);
            count++;
        }
    }
    for (int i = 0; i < P; i++) {
        for (long j = i; j < P; j++) {
            long a = (sosu[i] + sosu[j]);
            keep.push_back(a);
        }
    }

    // for (int i : keep) cout << i << " ";
    // cout << endl;

    sort(keep.begin(), keep.end());
    // cout << keep.size();
    return keep[P - 1];
    return 0;
}

int main(void) {
    int N, P;
    vector<int> ans;
    eratosu[0] = 0;
    eratosu[1] = 0;
    for (int i = 2; i * i < eratosu.size(); i++) {
        if (eratosu[i] == 1) {
            for (int j = 2 * i; j < eratosu.size(); j += i) {
                eratosu[j] = 0;
            }
        }
    }

    // for (int i : sosu) cout << i << " ";
    while (1) {
        cin >> N >> P;
        if (N == -1 && P == -1) break;
        ans.push_back(solve(N, P));
    }
    for (int i : ans) cout << i << 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;
            else if(n % i == 0){
                ans = 0;
                break;
            }
        }
    }
    return ans;
}

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

const int MAX = 1001000;

int main() {
	bool is_p[MAX] = {0};
	for ( int i = 2; i < MAX; i++ ) {
		for ( int j = 2; j*i < MAX; j++ ) {
			is_p[i*j] = true;
		}
	}

	vector<int> p;	
	for ( int i = 2; i < MAX; i++ ) {
		if ( !is_p[i] ) p.push_back(i);
	}
		
	int N, P;
	while ( cin >> N >> P, N != -1 ) {
		vector<int> v;
		int id = upper_bound(p.begin(), p.end(), N)-p.begin();
		//cout << p[id] << endl;
		for ( int i = id; i < id+110; i++ ) {			
			for ( int j = i; j < id+110; j++ ) {
				v.push_back(p[i]+p[j]);
			}
		}
		sort(v.begin(), v.end());
		cout << v[P-1] << endl;
	}

	return 0;
}

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

using namespace std;

int main() {
	vector<int> furui(101000, 0);
	furui[0] = furui[1] = 1;
	for (int i = 2; i * i <= 101000; i++) {
		if (furui[i] == 0) {
			for (int j = 2; j < 101000/i; j++) {
				furui[i*j] = 1;
			}
		}
	}
	int n, p;
	while (cin >> n >> p) {
		if (n == -1 && p == -1) {
			break;
		}
		int a = n+1;
		int counter = 0;
		while (counter == 0) {
			if (furui[a] == 0) {
				counter = a*2;
				break;
			} else {
				a++;
			}
		}
		int limit;
		int j = a;
		for (int i = 1; i < p; i++) {
			if (j == a) {
				counter++;
			}
			limit = counter/2;
			while (j <= limit) {
				if (furui[j] == 0 && furui[counter-j] == 0) {
					break;
				} else {
					j++;
				}
			}
			if (j > limit) {
				j = a;
				i--;
			} else {
				j++;
			}
		}
		cout << counter << endl;
	}
	return 0;
}

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

using namespace std;

int main()
{
	vector<int> isp(150001,1);
	isp[0]=isp[1]=0;
	for(int i=2;i*i<isp.size();i++)
		for(int j=i*i;j<isp.size();j+=i)
			isp[j]=0;
	vector<int> ps;
	for(int i=0;i<isp.size();i++) if(isp[i])
		ps.push_back(i);
	
	for(int n,p;cin>>n>>p,~(n&p);){
		vector<int> cs;
		int o=upper_bound(ps.begin(),ps.end(),n)-ps.begin();
		for(int i=0;i<p;i++)
			for(int j=i;j<p;j++)
				cs.push_back(ps[o+i]+ps[o+j]);
		sort(cs.begin(),cs.end());
		cout<<cs[p-1]<<endl;
	}
	
	return 0;
}