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<cstdio>
#include<string>
#include<algorithm>
#include<vector>
#include<unordered_set>
#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 <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[10000] = {0};
		if(isprime(n)) prime_array[0] = n;
		else prime_array[0] = min_prime(n);
		for(int i = 0; i < p; i++){
			prime_array[i + 1] = min_prime(prime_array[i]);
		}
		int k = 0;
		for(int i = 0; i < p; i++){
			for(int j = i; j < p; 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)
{
	int i = 1;
	while(1){
		if(isprime(n + i)) return n + i;
		else i++;
	}
}

int isprime(int n)
{
	int ans;
	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<iostream>
#include<algorithm>
#include<vector>
#include<set>
using namespace std;

const int MAX = 200100;

vector<int> primes;
bool isprime[MAX];

int main() {
  for (int i = 0; i < MAX; i++) {
    isprime[i] = true;
  }
  isprime[0] = isprime[1] = false;
  for (int n = 2; n < MAX; n++) {
    if (!isprime[n]) continue;
    primes.push_back(n);
    for (int m = n; m < MAX; m += n) {
      isprime[m] = false;
    }
  }

  int N, P;
  while (cin >> N >> P and N != -1) {
    auto iter = upper_bound(primes.begin(), primes.end(), N);
    set<int> s;
    cout << *iter;
    for (int i = 0; i < P; i++) {
      for (int j = i; j < P; j++) {
        s.insert(*(iter + i) + *(iter + j));
      }
    }
    vector<int> sums;
    for (int n : s) {
      sums.push_back(n);
    }
    cout << sums[P-1] << endl;
  }
}

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

int main() {
    vector<int> prime;
    array<bool, 2001000> is_prime;
    fill(is_prime.begin(), is_prime.end(), true);
    is_prime[0] = is_prime[1] = false;
    for(int i=2; i<is_prime.size(); ++i) {
        if(is_prime[i]) {
            prime.push_back(i);
            for(int j=i+i; j<is_prime.size(); j+=i) {
                is_prime[j] = false;
            }
        }
    }

    int N, P;
    while(cin >> N >> P, N != -1) {
        int idx = 0;
        while(N >= prime[idx]) {
            idx++;
        }
        vector<int> ans;
        for(int i=idx; i<idx+100; ++i) {
            for(int j=idx; j<=i; ++j) {
                ans.push_back(prime[i]+prime[j]);
            }
        }
        sort(ans.begin(), ans.end());
        cout << ans[P-1] << endl;
    }
}

C++: #include <bits/stdc++.h>
#include <stdint.h>

typedef uint32_t u32;
typedef uint64_t u64;

class Solver {
public:
  Solver();
  void solve(int N, int P);
private:
  bool isprime[200000];
};

Solver::Solver() {
  for(int i = 0; i < 200000; ++i) {
    isprime[i] = true;
  }
  isprime[0] = isprime[1] = false;
  for(int i = 2; i < 2000; ++i) {
    if( isprime[i] ) {
      for(int j = i * 2; j < 200000; j+=i) {
        isprime[j] = false;
      }
    }
  }
}

void Solver::solve(int N, int P) {
  std::vector<int> can;
  for(int i = N + 1; i < std::min(N + P * 4 + 1000, 200000); ++i) {
    if( not isprime[i] ) continue;
    for(int j = i; j < std::min(N + P * 4 + 1000, 200000); ++j) {
      if( not isprime[j] ) continue;
      can.push_back(i + j);
    }
  }
  std::sort(std::begin(can), std::end(can));
  std::cout << can[P-1] << std::endl;
}


int main() {

  Solver solver;
  
  for(;;) {
    int N, P;
    std::cin >> N >> P;
    if( N == -1 and P == -1 ) break;
    
    solver.solve(N, P);
  }  
  
  return 0;
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main(){
  int a,b;
  while(cin>>a>>b,a+b>0){
    int c[100],cnt=0;
    vector<int> ans;
    for(int i=a+1;cnt<100;i++){
      int cnt2=0;
      for(int j=2;j*j<=i;j++){
	if(i%j==0)cnt2++;
      }
      if(cnt2==0&&i!=1)c[cnt]=i,cnt++;
    }
    for(int i=0;i<100;i++)
      for(int j=i;j<100;j++)
	ans.push_back(c[i]+c[j]);
    sort(ans.begin(),ans.end());
    cout<<ans[b-1]<<endl;
  }
  return 0;
}