#include <iostream>
#include <cstdio>
#include <vector>
#include <cmath>
#include <map>
#include <algorithm>
#include <string>
#include <utility>
#include <set>
#include <stack>
#include <deque>
#include <ctime>
#include <random>
#include <cassert>
#include <cmath>
#include <climits>
#include <queue>
#include <cstring>
#include <bitset>
#include <iomanip>
#include <chrono>

/*
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("popcnt")
#pragma GCC target("avx2")
*/


#ifdef LOCAL
	#define dbg(x) cout << #x << " : " << x << endl;
#else 
	#define dbg(x)
#endif


#define int long long
#define fi(a,b) for (int i=a;i<b;i++)
#define fj(a,b) for (int j=a;j<b;j++)
#define fk(a,b) for (int k=a;k<b;k++)
#define fi1(a,b) for (int i=a-1;i>=b;i--)
#define fj1(a,b) for (int j=a-1;j>=b;j--)
#define fk1(a,b) for (int k=a-1;k>=b;k--)
#define fx(x,a) for (auto& x : a)
#define rep(i, a, b) for (int i = a; i < b; ++i)
#define rep1(i, a, b) for (int i = a - 1; i >= b; --i)
#define siz(x) (int)x.size()
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()

using namespace std;

template<typename T1, typename T2>inline void mine(T1 &x, T2 y) { if (x > y) x = y; }
template<typename T1, typename T2>inline void maxe(T1 &x, T2 y) { if (x < y) x = y; }

ostream& operator << (ostream &a, const vector<int> &b) {
    for (auto k : b) cout << k << ' ';
    return a;
}


typedef long long ll;
typedef unsigned long long ull;
typedef char ch;
typedef string str;
typedef pair<int, int> pii;
typedef map<int, int> mii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pii> vpii;
typedef vector<vpii> vvpii;
typedef vector<ch> vch;
typedef vector<vch> vvch;
typedef vector<str> vs;



const int MOD = 1000000007;
const int INF = 1000000050;
const long long BIG = (long long)2e18 + 50;
const int MX = 100010;
const double EPS = 1e-9;


mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());


int a[MX];
int n, m;

int calc(int x) {
	int l = 0;
	int r = n - 1;
	int res = 0;
	while (l < n) {
		while (r >= l && a[r] + a[l] < x)
			--r;
		res += 2 * max(0ll, r - l);
		if (a[l] + a[l] >= x)
			res++;
		++l;
	}
	return res;
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    cin >> n >> m;
    int sum = 0;
    fi(0, n) {
    	cin >> a[i];
    	sum += a[i];
    }
    sort(a, a + n);
    reverse(a, a + n);
    int l = -1;
    int r = 2 * MX;
    while(r - l > 1) {
    	int mid = (r + l) >> 1;
    	if (calc(mid) <= m)
    		r = mid;
    	else
    		l = mid;
    }
    int start = calc(r);
    reverse(a, a + n);
    int next = -BIG;
    fi(0, n) {
    	int sec = r - a[i];
    	auto it = lb(a, a + n, sec);
    	if (it != a)
    		maxe(next, a[i] + *--it); 
    }
    reverse(a, a + n);
    int ans = 0;
 	int left = 0;
 	int right = n - 1;
 	while (left < n) {
 		sum -= a[left];
 		while (right > left && a[right] + a[left] < r) {
 			sum -= a[right];
 			--right;
 		}
 		if (a[left] + a[left] >= r)
 			ans += (a[left] + a[left]);
 		if (right > left) {
 			ans += 2 * (right - left) * a[left];
 			ans += 2 * sum;
 		}
 		++left;
 	}
 	if (start != m)
 		ans += next * (m - start);
 	cout << ans << '\n';
}

Measured memory_bytes: 1024