#include <bits/stdc++.h>
using namespace std;
using ll = int_fast64_t;
const int mod = 1e9 + 7;
const int inf = (1 << 30) - 1;
const ll infll = (1LL << 61) - 1;
#define fast() ios::sync_with_stdio(false), cin.tie(nullptr)
#define digit(N) cout << fixed << setprecision((N))
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s)
{
    return '"' + s + '"';
}

string to_string(const char *s)
{
    return to_string((string)s);
}

string to_string(bool b)
{
    return (b ? "true" : "false");
}

string to_string(vector<bool> v)
{
    bool first = true;
    string res = "{";
    for (int i = 0; i < static_cast<int>(v.size()); i++)
    {
        if (!first)
        {
            res += ", ";
        }
        first = false;
        res += to_string(v[i]);
    }
    res += "}";
    return res;
}

template <size_t N>
string to_string(bitset<N> v)
{
    string res = "";
    for (size_t i = 0; i < N; i++)
    {
        res += static_cast<char>('0' + v[i]);
    }
    return res;
}

template <typename A>
string to_string(A v)
{
    bool first = true;
    string res = "{";
    for (const auto &x : v)
    {
        if (!first)
        {
            res += ", ";
        }
        first = false;
        res += to_string(x);
    }
    res += "}";
    return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p)
{
    return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p)
{
    return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p)
{
    return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T)
{
    cerr << " " << to_string(H);
    debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

#include <iostream>
#include <vector>
using namespace std;

vector<int> eratosthenes(int N)
{
    if (N < 2)
        return vector<int>();

    vector<int> res;
    vector<bool> prime(N + 1, 1);
    prime[0] = prime[1] = false;

    for (int i = 2; i * i <= N; ++i)
    {
        if (prime[i])
        {
            for (int j = 2 * i; j <= N; j += i)
            {
                prime[j] = false;
            }
        }
    }

    res.emplace_back(2);

    for (int i = 3; i <= N; i += 2)
    {
        if (prime[i] == true)
            res.emplace_back(i);
    }
    return res;
}

int main()
{
    fast();

    int N, P;

    auto primes = eratosthenes(500000);

    while (cin >> N >> P)
    {
        if (N == -1 && P == -1)
            return 0;

        int i = upper_bound(primes.begin(), primes.end(), N) - primes.begin();

        vector<int> st;

        for (int j = 0; j < 100; j++)
        {
            for (int k = j; k < 100; k++)
            {
                st.push_back(primes[i + j] + primes[i + k]);
            }
        }

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

        cout << st[P - 1] << "\n";
    }
}


Measured memory_bytes: 3316