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

typedef long long ll;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;
typedef vector<double> vd;
typedef vector<vd> vdd;

#define FOR(i,x,y) for(ll i=(ll)x; i<(ll)y; ++i)
#define REP(i,y) FOR(i, 0, y)
#define RFOR(i,x,y) for(ll i=(ll)x; i>=(ll)y; --i)
#define RREP(i,x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back
#define debug_print(x...) cerr << "line " << __LINE__ << " : "; debug_print_in(x);

template <typename First>
void debug_print_in(First first){
  cerr << first << endl;
  return;
}

template <typename First, typename... Rest>
void debug_print_in(First first, Rest... rest){
  cerr << first << " ";
  debug_print_in(rest...);
  return;
}

void IN(void){
  return;
}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}

template <typename First>
void OUT(First first){
  cout << first << endl;
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}

template<class t, class u> void chmax(t&a,u b){if(a<b)a=b;};
template<class t, class u> void chmin(t&a,u b){if(a>b)a=b;};
int popcount(int t){return __builtin_popcount(t);} //GCC
int popcount(ll t){return __builtin_popcountll(t);} //GCC

template <typename T>
void vec_print(vector<T> VEC){
  REP(i, VEC.size()){
    cerr << VEC[i] << " ";
  }
  cerr << endl;
};

template <typename T>
void mat_print(vector<vector<T> > MAT){
  REP(i,MAT.size()){
    REP(j,MAT[i].size()){
      cerr << MAT[i][j] << " ";
    }
    cerr << endl;
  }
};

constexpr int INF = (1<<30);
constexpr ll INFLL = 1LL<<62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9)+7);

class FFT{
  private:
    size_t sz;
    vector<complex<double>> tmp;
  public:
    FFT(void){};
    ~FFT(void){};

    vector<complex<double>> fft(vector<complex<double>> a, bool inv=false){
      size_t mask = sz-1;
      size_t p=0;
      for(size_t i=sz>>1; i>=1; i>>=1){
        auto& cur = (p&1) ? tmp : a;
        auto& nex = (p&1) ? a : tmp;
        complex<double> e = polar(1., 2*M_PI*i*(inv?-1:1)/sz);
        complex<double> w = 1;
        for(size_t j=0; j<sz; j+=i){
          for(size_t k=0; k<i; ++k){
            nex[j+k] = cur[((j<<1)&mask) + k] + w * cur[(((j<<1) + i) & mask) + k];
          }
          w *= e;
        }
        ++p;
      }
      if(p&1) swap(a,tmp);
      if(inv) for(size_t i=0; i<sz; ++i) a[i] /= sz;
      return a;
    }

    vll convoluve(vll a, vll b){
      size_t m = a.size() + b.size() - 1;
      sz = 1;
      while(m>sz) sz<<=1;
      tmp.resize(sz);
      vector<complex<double>> A(sz), B(sz);
      for(size_t i=0; i<a.size(); ++i) A[i].real(a[i]);
      for(size_t i=0; i<b.size(); ++i) B[i].real(b[i]);
      A = fft(A);
      B = fft(B);
      for(size_t i=0; i<sz; ++i) A[i] *= B[i];
      A = fft(A, true);
      a.resize(m);
      for(size_t i=0; i<m; ++i) a[i] = round(A[i].real());
      return a;
    }
};



int main(){
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after std::cin)
  ios::sync_with_stdio(false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  ll N, M;
  IN(N,M);
  vll A(1E5+1, 0);
  REP(i,N){
    ll T;
    IN(T);
    A[T]++;
  }
  
  vll B = A;

  FFT que;

  vll C = que.convoluve(A,B);

  ll tmp = 0;
  ll ans = 0;
  for(ll i=C.size()-1; i>=0; --i){
    if(tmp+C[i]<=M){
      tmp += C[i];
      ans += C[i]*i;
    }else{
      ans += (M-tmp)*i;
      tmp = M;
    }
  }

  OUT(ans);

  return 0;
}

Measured memory_bytes: 21880