#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep2(i, x, n) for (int i = x; i < (n); i++)
#define all(n) begin(n), end(n)
struct cww
{
    cww()
    {
        ios::sync_with_stdio(false);
        cin.tie(0);
    }
} star;
const long long INF = numeric_limits<long long>::max();
typedef long long ll;
typedef vector<int> vint;
typedef vector<char> vchar;
typedef vector<vector<int>> vvint;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef unsigned long long ull;
template <class T>
bool chmax(T &a, const T &b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b)
{
    if (b < a)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }

template <typename T, typename... Ts>
auto make_v(size_t a, Ts... ts)
{
    return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}
template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type
fill_v(T &t, const V &v) { t = v; }

template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type
fill_v(T &t, const V &v)
{
    for (auto &e : t)
        fill_v(e, v);
}
template <ll mod>
struct ModInt
{
    ll x;

    ModInt() : x(0) {}

    ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

    ModInt &operator+=(const ModInt &p)
    {
        if ((x += p.x) >= mod)
            x -= mod;
        return *this;
    }

    ModInt &operator-=(const ModInt &p)
    {
        if ((x += mod - p.x) >= mod)
            x -= mod;
        return *this;
    }

    ModInt &operator*=(const ModInt &p)
    {
        x = (ll)(1LL * x * p.x % mod);
        return *this;
    }

    ModInt &operator/=(const ModInt &p)
    {
        *this *= p.inverse();
        return *this;
    }

    ModInt operator-() const { return ModInt(-x); }

    ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }

    ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }

    ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }

    ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }

    bool operator==(const ModInt &p) const { return x == p.x; }

    bool operator!=(const ModInt &p) const { return x != p.x; }

    ModInt inverse() const
    {
        ll a = x, b = mod, u = 1, v = 0, t;
        while (b > 0)
        {
            t = a / b;
            swap(a -= t * b, b);
            swap(u -= t * v, v);
        }
        return ModInt(u);
    }

    ModInt pow(int64_t n) const
    {
        ModInt ret(1), mul(x);
        while (n > 0)
        {
            if (n & 1)
                ret *= mul;
            mul *= mul;
            n >>= 1;
        }
        return ret;
    }

    friend ostream &operator<<(ostream &os, const ModInt &p)
    {
        return os << p.x;
    }

    friend istream &operator>>(istream &is, ModInt &a)
    {
        int64_t t;
        is >> t;
        a = ModInt<mod>(t);
        return (is);
    }

    static int get_mod() { return mod; }
};

using modint = ModInt<(int)1e9 + 7>;

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); }
};

const real PI = acosl(-1);
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 = 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;
            }
        }
    }
}

vector<int64_t> multiply(const vector<int> &a, const vector<int> &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++)
    {
        int x = (i < (int)a.size() ? a[i] : 0);
        int 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;
}
}; // namespace FastFourierTransform

template <typename T>
struct FormalPowerSeries : vector<T>
{
    using vector<T>::vector;
    using P = FormalPowerSeries;
    using real = FastFourierTransform::real;
    using C = FastFourierTransform::C;
    using MULT = function<P(P, P)>;

    static P get_mult(const P &a, const P &b, int need = -1)
    {
        if (need == -1)
            need = a.size() + b.size() - 1;
        int nbase = 0;
        while ((1 << nbase) < need)
            nbase++;
        FastFourierTransform::ensure_base(nbase);
        int sz = 1 << nbase;
        vector<C> fa(sz);
        for (int i = 0; i < a.size(); i++)
        {
            fa[i] = C(a[i].x & ((1 << 15) - 1), a[i].x >> 15);
        }
        fft(fa, sz);
        vector<C> fb(sz);
        if (a == b)
        {
            fb = fa;
        }
        else
        {
            for (int i = 0; i < b.size(); i++)
            {
                fb[i] = C(b[i].x & ((1 << 15) - 1), b[i].x >> 15);
            }
            fft(fb, sz);
        }
        real ratio = 0.25 / sz;
        C r2(0, -1), r3(ratio, 0), r4(0, -ratio), r5(0, 1);
        for (int i = 0; i <= (sz >> 1); i++)
        {
            int j = (sz - i) & (sz - 1);
            C a1 = (fa[i] + fa[j].conj());
            C a2 = (fa[i] - fa[j].conj()) * r2;
            C b1 = (fb[i] + fb[j].conj()) * r3;
            C b2 = (fb[i] - fb[j].conj()) * r4;
            if (i != j)
            {
                C c1 = (fa[j] + fa[i].conj());
                C c2 = (fa[j] - fa[i].conj()) * r2;
                C d1 = (fb[j] + fb[i].conj()) * r3;
                C d2 = (fb[j] - fb[i].conj()) * r4;
                fa[i] = c1 * d1 + c2 * d2 * r5;
                fb[i] = c1 * d2 + c2 * d1;
            }
            fa[j] = a1 * b1 + a2 * b2 * r5;
            fb[j] = a1 * b2 + a2 * b1;
        }
        fft(fa, sz);
        fft(fb, sz);
        P ret(need);
        for (int i = 0; i < need; i++)
        {
            int64_t aa = llround(fa[i].x);
            int64_t bb = llround(fb[i].x);
            int64_t cc = llround(fa[i].y);
            aa = T(aa).x, bb = T(bb).x, cc = T(cc).x;
            ret[i] = aa + (bb << 15) + (cc << 30);
        }
        return ret;
    }
    P multx(const int k) const //x^kをかける
    {
        int deg = this->size();
        P tmp(deg + k);
        for (int i = 0; i < deg; i++)
        {
            tmp[i + k] = (*this)[i];
        }
        return tmp;
    }
    void shrink()
    {
        while (this->size() && this->back() == T(0))
            this->pop_back();
    }

    P operator+(const P &r) const { return P(*this) += r; }

    P operator+(const T &v) const { return P(*this) += v; }

    P operator-(const P &r) const { return P(*this) -= r; }

    P operator-(const T &v) const { return P(*this) -= v; }

    P operator*(const P &r) const { return P(*this) *= r; }

    P operator*(const T &v) const { return P(*this) *= v; }

    P operator/(const P &r) const { return P(*this) /= r; }

    P operator%(const P &r) const { return P(*this) %= r; }

    P &operator+=(const P &r)
    {
        if (r.size() > this->size())
            this->resize(r.size());
        for (int i = 0; i < r.size(); i++)
            (*this)[i] += r[i];
        return *this;
    }

    P &operator+=(const T &r)
    {
        if (this->empty())
            this->resize(1);
        (*this)[0] += r;
        return *this;
    }

    P &operator-=(const P &r)
    {
        if (r.size() > this->size())
            this->resize(r.size());
        for (int i = 0; i < r.size(); i++)
            (*this)[i] -= r[i];
        shrink();
        return *this;
    }

    P &operator-=(const T &r)
    {
        if (this->empty())
            this->resize(1);
        (*this)[0] -= r;
        shrink();
        return *this;
    }

    P &operator*=(const T &v)
    {
        const int n = (int)this->size();
        for (int k = 0; k < n; k++)
            (*this)[k] *= v;
        return *this;
    }

    P &operator*=(const P &r)
    {
        if (this->empty() || r.empty())
        {
            this->clear();
            return *this;
        }
        return *this = get_mult(*this, r);
    }

    P &operator%=(const P &r)
    {
        return *this -= *this / r * r;
    }

    P operator-() const
    {
        P ret(this->size());
        for (int i = 0; i < this->size(); i++)
            ret[i] = -(*this)[i];
        return ret;
    }

    P &operator/=(const P &r)
    {
        if (this->size() < r.size())
        {
            this->clear();
            return *this;
        }
        int n = this->size() - r.size() + 1;
        return *this = (rev().pre(n) * r.rev().inv(n)).pre(n).rev(n);
    }

    P pre(int sz) const
    {
        return P(begin(*this), begin(*this) + min((int)this->size(), sz));
    }

    P operator>>(int sz) const
    {
        if (this->size() <= sz)
            return {};
        P ret(*this);
        ret.erase(ret.begin(), ret.begin() + sz);
        return ret;
    }

    P operator<<(int sz) const
    {
        P ret(*this);
        ret.insert(ret.begin(), sz, T(0));
        return ret;
    }

    P rev(int deg = -1) const
    {
        P ret(*this);
        if (deg != -1)
            ret.resize(deg, T(0));
        reverse(begin(ret), end(ret));
        return ret;
    }

    P diff() const
    {
        const int n = (int)this->size();
        P ret(max(0, n - 1));
        for (int i = 1; i < n; i++)
            ret[i - 1] = (*this)[i] * T(i);
        return ret;
    }

    P integral() const
    {
        const int n = (int)this->size();
        P ret(n + 1);
        ret[0] = T(0);
        for (int i = 0; i < n; i++)
            ret[i + 1] = (*this)[i] / T(i + 1);
        return ret;
    }

    // F(0) must not be 0
    P inv(int deg = -1) const
    {
        assert(((*this)[0]) != T(0));
        const int n = (int)this->size();
        if (deg == -1)
            deg = n;
        P ret({T(1) / (*this)[0]});
        for (int i = 1; i < deg; i <<= 1)
        {
            ret = (ret + ret - ret * ret * pre(i << 1)).pre(i << 1);
        }
        return ret.pre(deg);
    }

    // F(0) must be 1
    P log(int deg = -1) const
    {
        assert((*this)[0] == 1);
        const int n = (int)this->size();
        if (deg == -1)
            deg = n;
        return (this->diff() * this->inv(deg)).pre(deg - 1).integral();
    }

    P sqrt(int deg = -1) const
    {
        const int n = (int)this->size();
        if (deg == -1)
            deg = n;

        if ((*this)[0] == T(0))
        {
            for (int i = 1; i < n; i++)
            {
                if ((*this)[i] != T(0))
                {
                    if (i & 1)
                        return {};
                    if (deg - i / 2 <= 0)
                        break;
                    auto ret = (*this >> i).sqrt(deg - i / 2) << (i / 2);
                    if (ret.size() < deg)
                        ret.resize(deg, T(0));
                    return ret;
                }
            }
            return P(deg, 0);
        }

        P ret({T(1)});
        T inv2 = T(1) / T(2);
        for (int i = 1; i < deg; i <<= 1)
        {
            ret = (ret + pre(i << 1) * ret.inv(i << 1)) * inv2;
        }
        return ret.pre(deg);
    }

    // F(0) must be 0
    P exp(int deg = -1) const
    {
        assert((*this)[0] == T(0));
        const int n = (int)this->size();
        if (deg == -1)
            deg = n;
        P ret({T(1)});
        for (int i = 1; i < deg; i <<= 1)
        {
            ret = (ret * (pre(i << 1) + T(1) - ret.log(i << 1))).pre(i << 1);
        }
        return ret.pre(deg);
    }

    P pow(int64_t k, int deg = -1) const
    {
        const int n = (int)this->size();
        if (deg == -1)
            deg = n;
        for (int i = 0; i < n; i++)
        {
            if ((*this)[i] != T(0))
            {
                T rev = T(1) / (*this)[i];
                P C(*this * rev);
                P D(n - i);
                for (int j = i; j < n; j++)
                    D[j - i] = C[j];
                D = (D.log() * k).exp() * (*this)[i].pow(k);
                P E(deg);
                if (i * k > deg)
                    return E;
                auto S = i * k;
                for (int j = 0; j + S < deg && j < D.size(); j++)
                    E[j + S] = D[j];
                return E;
            }
        }
        return *this;
    }

    T eval(T x) const
    {
        T r = 0, w = 1;
        for (auto &v : *this)
        {
            r += w * v;
            w *= x;
        }
        return r;
    }
};
using mint = ModInt<LONG_LONG_MAX>;
int main()
{
    ll N, M, ans = 0;
    cin >> N >> M;
    vll a(N);
    for (int i = 0; i < N; i++)
        cin >> a[i];
    FormalPowerSeries<mint> tmp(1e5 + 1);
    for (int i = 0; i < N; i++)
    {
        tmp[a[i]] += 1;
    }
    auto F = tmp * tmp;
    ll sz = F.size(), cnt = 0;
    for (ll i = sz - 1; i >= 0 and cnt < M; i--)
    {
        ans += min((M - cnt), (ll)F[i].x) * i;
        cnt += F[i].x;
    }
    cout << ans;

    return 0;
}

Measured memory_bytes: 17536