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

#define fs first
#define sc second
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define pb emplace_back

using pii = pair<int, int>;
using vi = vector<int>;
using lint = long long;

const int inf = 1001001001;
const lint linf = 1001001001001001001ll;
const int mod = 1e9 + 7;
const int dx[]{0, 1, 0, -1, -1, -1, 1, 1}, dy[]{1, 0, -1, 0, -1, 1, -1, 1};

template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; } return a > b; }
template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; } return a < b; }
template<typename T> inline void print(const T &x, string s = "\n") { cout << x << s; }
template<typename T> inline void print(const vector<T> &v, string s = " ") 
{ rep(i, v.size()) cout << v[i] << (i + 1 == v.size() ? "\n" : s); }
inline bool inside(int y, int x, int H, int W) { return 0 <= y && y < H && 0 <= x && x < W; }
inline lint in() { lint x; std::cin>>x; return x; }

lint gcd(lint a, lint b) {
	if (b == 0) return a;
	return gcd(b, a % b);
}

lint lcm(lint a, lint b) {
	return a / gcd(a, b) * b;
}

// ?????????????????????????????????????????????
lint extgcd(lint a, lint b, lint& x, lint& y) {
	lint d = a;
	if (b != 0) {
		d = extgcd(b, a % b, y, x);
		y -= (a / b) * x;
	} else {
		x = 1; y = 0;
	}
	return d;
}

bool is_prime(lint n) {
	if (n < 2) return false;
	for (lint i = 2; i * i <= n; ++i) {
		if (n % i == 0) return false;
	}
	return true;
}

// n????´???° ???????????????sorted
vector<lint> divisor(lint n) {
	vector<lint> res;
	deque<lint> d;

	lint i = sqrt(n);
	if (i * i == n) {
		d.push_back(i);
		i--;
	}
	for (; i > 0; --i) {
		if (n % i == 0){
			d.push_front(i);
			d.push_back(n / i);
		}
	}

	res.insert(res.begin(), d.begin(), d.end());
	return res;
}


// 2 * 2 * 3 * 5 * 5 * 5 = {2:2, 3:1,5:3} ???????????? map ?????????
map<int, int> prime_mod_factor(lint n) {
	map<int, int> res;
	for (int i = 2; i * i <= n; ++i) {
		while (n % i == 0) {
			++res[i];
			n /= i;
		}
	}

	if (n != 1) res[n] = 1;
	return res;
}

const int MAX_N = 2020202;
vi prime;
bool memo[MAX_N + 1];

// ?´???°?????¨?????? n??\???????´???°????????°?????????
int sieve(int n) {
	prime.clear();
	memset(memo, true, sizeof(memo));
	memo[0] = memo[1] = false;

	for (int i = 2; i <= n; ++i) {
		if (memo[i]) {
			prime.pb(i);
			for (int j = i + i; j <= n; j += i) {
				memo[j] = false;
			}
		}
	}

	return prime.size();
}

const lint MAX_LEN = 1000000;
const lint MAX_SQRT_B = 1000000;
bool memo_alint[MAX_LEN];         //i means i + a
bool memo_smalint[MAX_SQRT_B];

// [a, b)????´???°????????°???????????????
lint count_prime(lint a, lint b) {
	for (int i = 0; (lint)i * i < b; i++) memo_smalint[i] = true;
	for (int i = 0; i < b - a; i++)     memo_alint[i] = true;

	for (int i = 2; (lint)i * i < b; i++) {
		if (memo_smalint[i]) {
			for (int j = 2; (lint)j * j < b; j += i) memo_smalint[j] = false;
			for (lint j = max(2LL, (a + i - 1) / i) * i; j < b; j += i) memo_alint[j - a] = false;
		}
	}

	lint ret = 0;
	for (lint i = a; i < b; i++) {
		if (memo_alint[i]) ret++;
	}
	return ret;
}

// k???????????§????????£??????????????°??????{a_0 : 0, a_1 : 1, a_2 : 1, ... }
lint Fib[101010];
int calcFib(int k) {
	Fib[0] = 0;
	Fib[1] = Fib[2] = 1;
	for (int i = 3; i <= k; ++i) {
		Fib[i] = Fib[i - 1] + Fib[i - 2];
		// Fib[i] %= mod;
	}

	return Fib[k];
}

lint mod_pow(lint a, lint x) {
	lint ret = 1;
	for (lint i  = 1ll << 60; i; i >>= 1) {
		ret *= ret;
		ret %= mod;
		if (x & i) { ret *= a; ret %= mod; }
	}

	return ret;
}

lint mod_fact(lint n) {
	lint ret = 1;
	for (lint i = 1; i <= n; ++i) {
		ret *= i;
		ret %= mod;
	}
	return ret;
}

lint mod_inverse(lint n) {
	return mod_pow(n, mod - 2);
}

// nCk ???mod
lint mod_Combination(lint n, lint k) {
	return mod_fact(n) * mod_inverse(mod_fact(k)) % mod * mod_inverse(mod_fact(n - k)) % mod;
}

int main() {
	sieve(MAX_N);
	//print(prime);

	int n, p;
	while (cin >> n >> p) {
		if (n == -1) break;
		
		vi a;
		for (int i = n + 1; a.size() < 110; ++i) {
			if (memo[i]) a.pb(i);
		}

	//	print(a);

		vi ans;
		rep(i, a.size()) for (int j = i; j < a.size(); ++j) {
			ans.pb(a[i] + a[j]);
		}

		sort(all(ans));

		print(ans[p - 1]);
	}
}

Measured memory_bytes: 5804