#include <bits/stdc++.h>
using namespace std;
#ifndef ONLINE_JUDGE
	#include <boost/multiprecision/cpp_int.hpp>
	#include <boost/multiprecision/cpp_dec_float.hpp>
	using bll = boost::multiprecision::cpp_int;
	using bdouble = boost::multiprecision::cpp_dec_float_100;
#endif
#ifdef LOCAL_DEV
	void debug_impl() { std::cerr << std::endl; }
	template<typename Head, typename... Tail> void debug_impl(Head head, Tail... tail) { std::cerr << " " << head << (sizeof...(tail) ? "," : ""); debug_impl(tail...); }
	#define debug(...) { std::cerr << std::boolalpha << "(" << #__VA_ARGS__ << ") ="; debug_impl(__VA_ARGS__); std::cerr << std::noboolalpha; }
#else
	#define debug(...) {}
#endif
#ifdef LOCAL_TEST
	#define BOOST_STACKTRACE_USE_ADDR2LINE
	#define BOOST_STACKTRACE_ADDR2LINE_LOCATION /usr/local/opt/binutils/bin/addr2line
	#define _GNU_SOURCE
	#include <boost/stacktrace.hpp>
	template<typename T> class dvector : public std::vector<T> {
	public:
		dvector() : std::vector<T>() {}
		explicit dvector(size_t n, const T& value = T()) : std::vector<T>(n, value) {}
		dvector(const std::vector<T>& v) : std::vector<T>(v) {}
		dvector(const std::initializer_list<T> il) : std::vector<T>(il) {}
		dvector(const typename std::vector<T>::iterator first, const typename std::vector<T>::iterator last) : std::vector<T>(first, last) {}
		dvector(const std::string::iterator first, const std::string::iterator last) : std::vector<T>(first, last) {}
		T& operator[](size_t n) {
			try { return this->at(n); } catch (const std::exception& e) {
				std::cerr << boost::stacktrace::stacktrace() << std::endl; return this->at(n);
			}
		}
		const T& operator[](size_t n) const {
			try { return this->at(n); } catch (const std::exception& e) {
				std::cerr << boost::stacktrace::stacktrace() << std::endl; return this->at(n);
			}
		}
	};
	class dbool {
	private:
		bool boolvalue;
	public:
		dbool() : boolvalue(false) {}
		dbool(bool b) : boolvalue(b) {}
		dbool(const dbool &b) : boolvalue(b.boolvalue) {}
		operator bool&() { return boolvalue; }
		operator const bool&() const { return boolvalue; }
	};
	template<typename T> std::ostream& operator<<(std::ostream& s, const dvector<T>& v) {
		for (int i = 0, len = v.size(); i < len; ++i){ s << v[i]; if (i < len - 1) s << "\t"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const dvector< dvector<T> >& vv) {
		for (int i = 0, len = vv.size(); i < len; ++i){ s << vv[i] << std::endl; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::set<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::multiset<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::map<T1, T2>& m) {
		s << "{" << std::endl; for (auto itr = m.begin(); itr != m.end(); ++itr){ s << "\t" << (*itr).first << " : " << (*itr).second << std::endl; } s << "}"; return s; }
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::pair<T1, T2>& p) { 
		return s << "(" << p.first << ", " << p.second << ")"; }
	#define vector dvector
	#define bool dbool
	class SIGFPE_exception : std::exception {};
	class SIGSEGV_exception : std::exception {};
	void catch_SIGFPE(int e) { std::cerr << boost::stacktrace::stacktrace() << std::endl; throw SIGFPE_exception();	}
	void catch_SIGSEGV(int e) { std::cerr << boost::stacktrace::stacktrace() << std::endl; throw SIGSEGV_exception(); }
	signed convertedmain();
	signed main() { signal(SIGFPE, catch_SIGFPE); signal(SIGSEGV, catch_SIGSEGV); return convertedmain(); }
	#define main() convertedmain()
#endif
//#define int long long
using ll = long long;
//constexpr int INF = 1e9;//INT_MAX=(1<<31)-1=2147483647
constexpr ll INF = (ll)1e18;//(1LL<<63)-1=9223372036854775807
constexpr ll MOD = (ll)1e9 + 7;
constexpr double EPS = 1e-9;
constexpr int dx[4] = {1, 0, -1, 0};
constexpr int dy[4] = {0, 1, 0, -1};
constexpr int dx8[8] = {1, 0, -1, 0, 1, 1, -1, -1};
constexpr int dy8[8] = {0, 1, 0, -1, 1, -1, 1, -1};
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define rrep(i, n)   for(ll i=(n)-1; i>=0; --i)
#define rrepeq(i, n) for(ll i=(n)  ; i>=1; --i)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define uniq(v) (v).erase(unique((v).begin(), (v).end()), (v).end())
void p() { std::cout << '\n'; }
template<typename Head, typename... Tail> void p(Head head, Tail... tail) { std::cout << head << (sizeof...(tail) ? " " : ""); p(tail...); }
template<typename T> inline void pv(vector<T> &v) { for(ll i=0, N=v.size(); i<N; i++) std::cout << v[i] << " \n"[i==N-1]; }
template<typename T> inline T gcd(T a, T b) { return b ? gcd(b,a%b) : a; }
template<typename T> inline T lcm(T a, T b) { return a / gcd(a,  b) * b; }
template<typename T> inline bool chmax(T &a, T b) { return a < b && (a = b, true); }
template<typename T> inline bool chmin(T &a, T b) { return a > b && (a = b, true); }

/*-----8<-----template-----8<-----*/

//計算量 O((n+m)log(n+m))
namespace FastFourierTransform {
	using real = double;

	struct C {
		real x, y;
		C() : x(0), y(0) {}
		C(real x, real y) : x(x), y(y) {}
		inline C operator+(const C &c) const { return C(x + c.x, y + c.y); }
		inline C operator-(const C &c) const { return C(x - c.x, y - c.y); }
		inline C operator*(const C &c) const { return C(x * c.x - y * c.y, x * c.y + y * c.x); }
		inline C conj() const { return C(x, -y); }
	};

	int base = 1;
	vector< C > rts = {{0, 0},
						{1, 0}};
	vector< int > rev = {0, 1};

	void ensure_base(int nbase) {
		if(nbase <= base) return;
		rev.resize(1 << nbase);
		rts.resize(1 << nbase);
		for(int i = 0; i < (1 << nbase); i++) {
			rev[i] = (rev[i >> 1] >> 1) + ((i & 1) << (nbase - 1));
		}
		while(base < nbase) {
			real angle = M_PI * 2.0 / (1 << (base + 1));
			for(int i = 1 << (base - 1); i < (1 << base); i++) {
				rts[i << 1] = rts[i];
				real angle_i = angle * (2 * i + 1 - (1 << base));
				rts[(i << 1) + 1] = C(cos(angle_i), sin(angle_i));
			}
			++base;
		}
	}

	void fft(vector< C > &a, int n) {
		assert((n & (n - 1)) == 0);
		int zeros = __builtin_ctz(n);
		ensure_base(zeros);
		int shift = base - zeros;
		for(int i = 0; i < n; i++) {
			if(i < (rev[i] >> shift)) {
				swap(a[i], a[rev[i] >> shift]);
			}
		}
		for(int k = 1; k < n; k <<= 1) {
			for(int i = 0; i < n; i += 2 * k) {
				for(int j = 0; j < k; j++) {
					C z = a[i + j + k] * rts[j + k];
					a[i + j + k] = a[i + j] - z;
					a[i + j] = a[i + j] + z;
				}
			}
		}
	}

	template<typename T>
	vector< int64_t > multiply(vector< T > &a, vector< T > &b) {
		int need = (int) a.size() + (int) b.size() - 1;
		int nbase = 1;
		while((1 << nbase) < need) nbase++;
		ensure_base(nbase);
		int sz = 1 << nbase;
		vector< C > fa(sz);
		for(int i = 0; i < sz; i++) {
			real x = (i < (int) a.size() ? a[i] : 0);
			real y = (i < (int) b.size() ? b[i] : 0);
			fa[i] = C(x, y);
		}
		fft(fa, sz);
		C r(0, -0.25 / (sz >> 1)), s(0, 1), t(0.5, 0);
		for(int i = 0; i <= (sz >> 1); i++) {
			int j = (sz - i) & (sz - 1);
			C z = (fa[j] * fa[j] - (fa[i] * fa[i]).conj()) * r;
			fa[j] = (fa[i] * fa[i] - (fa[j] * fa[j]).conj()) * r;
			fa[i] = z;
		}
		for(int i = 0; i < (sz >> 1); i++) {
			C A0 = (fa[i] + fa[i + (sz >> 1)]) * t;
			C A1 = (fa[i] - fa[i + (sz >> 1)]) * t * rts[(sz >> 1) + i];
			fa[i] = A0 + A1 * s;
		}
		fft(fa, sz >> 1);
		vector< int64_t > ret(need);
		for(int i = 0; i < need; i++) {
			ret[i] = llround(i & 1 ? fa[i >> 1].y : fa[i >> 1].x);
		}
		return ret;
	}
};

/*-----8<-----library-----8<-----*/

const ll N_MAX = 1e5;
const ll A_I_MAX = 1e5;

ll N, M;
vector<ll> A;

void solve() {
	scanf("%lld%lld", &N, &M);
	A.assign(N, 0);
	rep(i, N) { scanf("%lld", &A[i]); }

	ll ans = 0;

	vector< ll > x((ll)1e5+1, 0), y((ll)1e5+1, 0);
	for(ll i = 0; i < N; i++) x[A[i]]++;
	for(ll i = 0; i < N; i++) y[A[i]]++;

	ll m=M;
	vector<int64_t> C = FastFourierTransform::multiply(x, y);
	rrep(i,C.size()){
		if(!C[i])continue;
		if(C[i]<m){
			ans+=C[i]*i;
			m-=C[i];
		}else{
			ans+=m*i;
			break;
		}
	}
	printf("%lld\n", ans);
}

// https://atcoder.jp/contests/abc149/tasks/abc149_e
signed main() {
	solve();
	return 0;
}


Measured memory_bytes: 13440