#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <limits>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <functional>
#include <iomanip>

using namespace std;

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define eprintf(...) 42
#endif
using ll = long long;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vvvll = std::vector<vvll>;
#define reps(i, S, E) for (ll i = (S); i <= (E); i++)
#define rep(i, N) reps(i, 0, N-1)
#define deps(i, E, S) for (ll i = (E); i >= (S); i--)
#define dep(i, N) deps(i, N-1, 0)
const ll INF = 1LL << 60;
const int INF_INT = 1 << 30;

template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }
struct mll {
	static ll MOD;
	ll val;
	mll(ll v = 0) : val(v % MOD) { if (val < 0) val += MOD; }
	mll operator - () const { return -val; }
	mll operator + (const mll &b) const { return val + b.val; }
	mll operator - (const mll &b) const { return val - b.val; }
	mll operator * (const mll &b) const { return val * b.val; }
	mll operator / (const mll &b) const { return mll(*this) /= b; }
	mll operator + (ll b) const { return *this + mll(b); }
	mll operator - (ll b) const { return *this - mll(b); }
	mll operator * (ll b) const { return *this * mll(b); }
	friend mll operator + (ll a, const mll &b) { return b + a; }
	friend mll operator - (ll a, const mll &b) { return -b + a; }
	friend mll operator * (ll a, const mll &b) { return b * a; }
	mll &operator += (const mll &b) { val = (val + b.val) % MOD; return *this; }
	mll &operator -= (const mll &b) { val = (val + MOD - b.val) % MOD; return *this; }
	mll &operator *= (const mll &b) { val = (val*b.val) % MOD; return *this; }
	mll &operator /= (const mll &b) {
		ll c = b.val, d = MOD, u = 1, v = 0;
		while (d) {
			ll t = c / d;
			c -= t * d; swap(c, d);
			u -= t * v; swap(u, v);
		}
		val = val * u % MOD;
		if (val < 0) val += MOD;
		return *this;
	}
	mll &operator += (ll b) { return *this += mll(b); }
	mll &operator -= (ll b) { return *this -= mll(b); }
	mll &operator *= (ll b) { return *this *= mll(b); }
	mll &operator /= (ll b) { return *this /= mll(b); }
	bool operator == (const mll &b) { return val == b.val; }
	bool operator != (const mll &b) { return val != b.val; }
	bool operator == (ll b) { return *this == mll(b); }
	bool operator != (ll b) { return *this != mll(b); }
	friend bool operator == (ll a, const mll &b) { return mll(a) == b.val; }
	friend bool operator != (ll a, const mll &b) { return mll(a) != b.val; }
	friend ostream &operator << (ostream &os, const mll &a) { return os << a.val; }
	friend istream &operator >> (istream &is, mll &a) { return is >> a.val; }
	static mll Combination(ll a, ll b) {
		chmin(b, a - b);
		if (b < 0) return mll(0);
		mll c = 1;
		rep(i, b) c *= a - i;
		rep(i, b) c /= i + 1;
		return c;
	}
};
using vmll = std::vector<mll>;
using vvmll = std::vector<vmll>;
using vvvmll = std::vector<vvmll>;
using vvvvmll = std::vector<vvvmll>;

struct Fast {
	Fast() {
		cin.tie(0);
		ios::sync_with_stdio(false);
		cout << fixed << setprecision(std::numeric_limits<double>::max_digits10);
	}
} fast; //cin,cout�������̂��܂��Ȃ��{�����w��

ll mll::MOD = (ll)(1e9 + 7);// 998244353ll;


//E
ll N;
ll M;
vector<ll> A;
vll scoreCumulativeHistogram;
vll combCount;

// index �������𖞂������ǂ���
bool isOK(ll index, ll key) { //index�ȏ�̑g�ݍ��킹��key�ȏ゠�邩�H
	ll comb = 0;
	rep(i, N) {
		//A[i]�Ƒg�ݍ��킹�邱�Ƃ�index�ȏ�ƂȂ�����v��
		ll neededCount = max(1ll, index - A[i]); //�Œ��1
		if (neededCount > 100000) {
			continue; //���̓_���͑��݂��Ȃ�
		}
		comb += scoreCumulativeHistogram[neededCount];
	}

	combCount[index] = comb; //�ۑ����Ă���

	if (comb >= key) {
		return true;
	}
	else {
		return false;
	}
}

// �ėp�I�ȓ񕪒T���̃e���v��
ll binary_search(ll key) {
	ll ng = 200001;
	ll ok = -1;

	// ok �� ng �̂ǂ��炪�傫�����킩��Ȃ����Ƃ��l��
	while (abs(ok - ng) > 1) {
		ll mid = (ok + ng) / 2;
		if (isOK(mid, key)) {
			ok = mid;
		}
		else {
			ng = mid;
		}
	}
	return ok;
}

int main() {
	cin >> N;
	cin >> M;
	A.resize(N);
	rep(i, N) {
		cin >> A[i];
	}

	std::sort(A.begin(), A.end(), std::greater<ll>());
	scoreCumulativeHistogram.resize(100010);
	rep(i, 100010) {
		scoreCumulativeHistogram[i] = 0;
	}
	vll gainCumulativeHistogram(100010, 0);

	rep(i, N) {
		scoreCumulativeHistogram[A[i]]++;
		gainCumulativeHistogram[A[i]] += A[i];
	}

	deps(i, 100000, 1) {
		scoreCumulativeHistogram[i] += scoreCumulativeHistogram[i + 1];
		gainCumulativeHistogram[i] += gainCumulativeHistogram[i + 1];
	}

	combCount.resize(200001);
	rep(i, 200001) {
		combCount[i] = 0;
	}

	ll okGain = binary_search(M);
	ll ngGain = okGain + 1;
	eprintf("okGain:%lld ngGain:%lld\n", okGain, ngGain);
	eprintf("score\n");
	reps(i, 1, 70) {
		eprintf("%lld ", scoreCumulativeHistogram[i]);
	}
	eprintf("\ngain\n");
	reps(i, 1, 70) {
		eprintf("%lld ", gainCumulativeHistogram[i]);
	}
	eprintf("\ncombCount\n");
	reps(i, 1, 70) {
		eprintf("%lld ", combCount[i]);
	}
	eprintf("\n");

	ll result = 0;

	if (combCount[okGain] == M) {
		rep(i, N) {
			//A[i]�Ƒg�ݍ��킹�邱�Ƃ�okGain�ȏ�ƂȂ�g�ݍ��킹�𑫂����킹��
			ll neededPoint = max(1ll, okGain - A[i]); //�Œ��1
			if (neededPoint > 100000) {
				continue; //���̓_���͑��݂��Ȃ�
			}

			if (scoreCumulativeHistogram[neededPoint] == 0) {
				continue;
			}

			result += scoreCumulativeHistogram[neededPoint] * A[i]; //�g�ݍ��킹��=���̓_x�g�ݍ��킹��̌�
			result += gainCumulativeHistogram[neededPoint]; //�g�ݍ��킹��
		}
	}
	else {
		rep(i, N) {
			//A[i]�Ƒg�ݍ��킹�邱�Ƃ�ngGain�ȏ�ƂȂ�g�ݍ��킹�𑫂����킹��
			ll neededPoint = max(1ll, ngGain - A[i]); //�Œ��1
			if (neededPoint > 100000) {
				continue; //���̓_���͑��݂��Ȃ�
			}

			if (scoreCumulativeHistogram[neededPoint] == 0) {
				continue;
			}

			result += scoreCumulativeHistogram[neededPoint] * A[i]; //�g�ݍ��킹��=���̓_x�g�ݍ��킹��̌�
			result += gainCumulativeHistogram[neededPoint]; //�g�ݍ��킹��
		}

		ll lastM = M - combCount[ngGain];

		result += lastM * okGain; //okGain��ngGain�̍���1�Ȃ̂ŁA�c��̂����ōł�Gain�������Ȃ�̂�okGain�ƂȂ�
	}

	cout << result << endl;

	return 0;
}

/*
struct LLPair {
	ll a = 0;
	ll b = 0;
	ll m = 0;
	LLPair() {}
	LLPair(ll a, ll b, ll m) {
		this->a = a;
		this->b = b;
		this->m = m;
	}
	bool operator<(const LLPair &c) const {
		return m < c.m;
	}
};


struct LLPair2 {
	ll a = 0;
	ll b = 0;
	LLPair2() {}
	LLPair2(ll a, ll b) {
		this->a = a;
		this->b = b;
	}
	bool operator<(const LLPair2 &c) const {
		return a * 100000 + b < c.a * 100000 + c.b;
	}
};

int main() {
	ll N;
	cin >> N;
	ll M;
	cin >> M;
	vector<ll> A(N);
	rep(i, N) {
		cin >> A[i];
	}

	std::sort(A.begin(), A.end(), std::greater<ll>());

	ll result = 0;

	priority_queue<LLPair> pq;

	ll sqrtM = (ll)sqrt((double)M);
	sqrtM--;

	rep(i, sqrtM) {
		result += A[i] * 2 * sqrtM;
	}

	rep(i, sqrtM) {
		pq.push(LLPair(i, sqrtM, A[i] + sqrtM));
	}

	ll lastM = M - sqrtM * sqrtM;

	set<LLPair2> st;

	while (lastM > 0) {
		auto next = pq.top();
		pq.pop();

		if (next.a != next.b) {
			if (lastM >= 2) {
				result += next.m * 2;
				lastM -= 2;
			}
			else {
				result += next.m;
				lastM--;
			}

			if (next.a < N - 1) {
				auto a = LLPair2(next.a + 1, next.b);
				if (st.find(a) != st.end()) {
					st.insert(a);
					pq.push(LLPair(next.a + 1, next.b, A[next.a + 1] + A[next.b]));
				}

			}

			if (next.b < next.a) {
				auto a = LLPair2(next.a, next.b + 1);
				if (st.find(a) != st.end()) {
					st.insert(a);
					pq.push(LLPair(next.a, next.b + 1, A[next.a] + A[next.b + 1]));
				}

			}
		}
		else {
			result += next.m;
			lastM--;
		}


	}


	cout << result << endl;

	return 0;
}
*/

//D
/*
int main() {
	ll N;
	cin >> N;
	ll K;
	cin >> K;
	ll R;
	cin >> R;
	ll S;
	cin >> S;
	ll P;
	cin >> P;
	string T;
	cin >> T;
	ll len_T = T.size();

	ll result = 0;
	vector<bool> aiko(N, false);

	rep(i, N) {
		if (i < K) {
			if (T[i] == 'r') {
				result += P;
			}
			else if (T[i] == 's') {
				result += R;
			}
			else {
				result += S;
			}
		}
		else {
			if (T[i] == T[i - K] && aiko[i - K] == false) {
				//aiko
				aiko[i] = true;
			}
			else if (T[i] == 'r') {
				result += P;
			}
			else if (T[i] == 's') {
				result += R;
			}
			else {
				result += S;
			}
		}
	}

	cout << result << endl;

	return 0;
}
*/

//C
/*
bool Prime(ll x) {
	if (x == 1 || x == 2) {
		return true;
	}
	if (x % 2 == 0) {
		return false;
	}
	for (ll i = 3; i <= (ll)std::sqrt(x); i += 2) {
		if (x % i == 0) {
			return false;
		}
	}
	return true;
}

int main() {
	ll X;
	cin >> X;

	ll result = 0;

	while (true) {
		if (Prime(X)) {
			result = X;
			break;
		}

		X++;
	}

	cout << result << endl;

	return 0;
}
*/

//B
/*
int main() {
	ll A;
	cin >> A;
	ll B;
	cin >> B;
	ll K;
	cin >> K;

	if (K >= A) {
		K -= A;
		A = 0;

		B = max(0ll, B - K);
	}
	else {
		A -= K;
	}

	cout << A << " " << B << endl;

	return 0;
}
*/

//A
/*
int main() {
	string s;
	cin >> s;
	ll len_s = s.size();
	string t;
	cin >> t;
	ll len_t = t.size();

	string result = t + s;

	cout << result << endl;

	return 0;
}
*/

Measured memory_bytes: 4224