This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define ff first
#define ss second
ll ttt;
const ll INF=1e18;
const ll MOD=1e9+7;
const ll N=300007;
ll n,m,k;
ll a[N];
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    // freopen("output.txt","w",stdout);
    // freopen("input.txt","r",stdin);
    cin>>n>>m;
    for(int i=0;i<n;i++){
        int x;
        cin>>x;
        a[x]++;
    }
    cin>>m>>m;
    vector<ll>d;
    for(int i=0;i<N;i++){
        if(a[i])d.push_back(a[i]);
    }
    sort(d.begin(),d.end());
    vector<ll>p(d.size(),0);
    for(int i=0;i<d.size();i+=2){
        p[i/2]=d[i];
        if(i+1!=d.size())p[d.size()-i/2-1]=d[i+1];
    }
    ll ans=0;
    for(int i=0;i<p.size();i++){
        ans+=(p[i]*(p[i]+1))/2;
        for(int j=1;i+j<p.size();j++){
            ans+=p[i]*p[i+j]*(j+1);
        }
    }
    cout<<ans<<endl;
}
Compilation message (stderr)
diversity.cpp: In function 'int main()':
diversity.cpp:38:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |     for(int i=0;i<d.size();i+=2){
      |                 ~^~~~~~~~~
diversity.cpp:40:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 |         if(i+1!=d.size())p[d.size()-i/2-1]=d[i+1];
      |            ~~~^~~~~~~~~~
diversity.cpp:43:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   43 |     for(int i=0;i<p.size();i++){
      |                 ~^~~~~~~~~
diversity.cpp:45:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   45 |         for(int j=1;i+j<p.size();j++){
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