Language: C++

#include<bits/stdc++.h>
using namespace std;
#define FOR(i,a,b)  for(int i=(a),i##formax=(b);i< i##formax;i++)
#define FORR(i,a,b) for(int i=(a),i##formin=(b);i>=i##formin;i--)
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define pcnt __builtin_popcount
#define sz(x) (int)(x).size()
#define maxs(x,y) x=max((x),(y))
#define mins(x,y) x=min((x),(y))
#define show(x) cout<<#x<<" = "<<(x)<<endl;
#define all(a) ((a).begin()),((a).end())
#define each(i,c) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();i++)
#define bit(n) (1LL<<(n))
typedef long long ll;
typedef __int128_t lll;
template<class T>using V=vector<T>;
template<class T>using VV=V<V<T>>;
template<class T,class Y>using P=pair<T,Y>;
template<class T,class Y>ostream& operator<<(ostream&o,P<T,Y>&p){return o<<"("<<p.fi<<","<<p.se<<")";}
template<class T>ostream& operator<<(ostream&o,V<T>&v){for(T&t:v)o<<t<<",";return o<<endl;}
template<class T>void uniq(V<T>&v){sort(all(v));v.erase(unique(all(v)), v.end());}

lll gcd(lll a,lll b,lll&x,lll&y){if(!b){x=1;y=0;return a;}lll d=gcd(b,a%b,y,x);y-=a/b*x;return d;}
ll modInv(ll a,ll m){lll x,y;gcd(a,m,x,y);return(x%m+m)%m;}
ll modPow(lll a,lll n,ll m){lll p=1;for(;n;n>>=1,a=a*a%m)if(n&1)p=p*a%m;return p;}
//V<ll>F,R;void setF(int n,int mod){F=R=V<ll>(++n);F[0]=1;FOR(i,1,n)F[i]=F[i-1]*i%mod;R[n-1]=modInv(F[n-1],mod);FORR(i,n-1,1)R[i-1]=R[i]*i%mod;}
//ll comb(int a,int b,int m){return a<b||b<0?0:F[a]*R[b]%m*R[a-b]%m;}

const int IINF = 1e9+6;
const ll LINF = 1e18;
const int MOD = 1e9+7; //998244353;
const int N = 1e5;
ll a[N];
ll n, m, c[N+1], s[N+1];
main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cin >> n >> m;
  FOR(i, 0, n){
    cin >> a[i];
    c[a[i]]++;
    s[a[i]] += a[i];
  }
  FORR(i, N-1, 0){
    s[i] += s[i+1];
    c[i] += c[i+1];
  }
  ll l = -1, r = IINF, k;
  ll ans;
  while(r-l>1){
    k = (l+r)/2;
    ll cc = 0, ss = 0;
    FOR(i, 0, n){
      ll t = max(0, min(k-a[i], N));
      cc += c[t];
      ss += s[t]+c[t]*a[i];
    }
    if(cc < m){
      r = k;
    }else{
      l = k;
      ans = ss-(cc-m)*k;
    }
  }
  cout << ans << endl;
}


Compiler output:
a.cc:38:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   38 | main(){
      | ^~~~
a.cc: In function 'int main()':
a.cc:57:24: error: no matching function for call to 'min(ll, const int&)'
   57 |       ll t = max(0, min(k-a[i], N));
      |                     ~~~^~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:233:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::min(const _Tp&, const _Tp&)'
  233 |     min(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note:   template argument deduction/substitution failed:
a.cc:57:24: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'int')
   57 |       ll t = max(0, min(k-a[i], N));
      |                     ~~~^~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::min(const _Tp&, const _Tp&, _Compare)'
  281 |     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5686:5: note: candidate: 'template<class _Tp> constexpr _Tp std::min(initializer_list<_Tp>)'
 5686 |     min(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5686:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5696:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::min(initializer_list<_Tp>, _Compare)'
 5696 |     min(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5696:5: note:   template argument deduction/substitution failed:
a.cc:57:24: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   57 |       ll t = max(0, min(k-a[i], N));
      |                     ~~~^~~~~~~~~~~