#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
vector <int> v;
int cautare_binara(int l,int r,int nr)
{
    int mij;
    while(l<r)
    {
        mij=(l+r)/2;
        if(v[mij]<=nr)
        {
            l=mij+1;
        }
        else
        {
            r=mij;
        }
    }
    mij=(l+r)/2;
    if(v[mij]>nr)
    {
        mij--;
    }
    return mij;
}
int main()
{
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    int n,i,j,s_laturi,pos,nr,counter=0;
    fin>>n;
    for(i=0;i<=n-1;i++)
    {
        cin>>nr;
        v.push_back(nr);
    }
    sort(v.begin(),v.end());
    for(i=0;i<=n-2;i++)
    {for(j=i+1;j<=n-1;j++)
      {
          s_laturi=v[i]+v[j];
          pos=cautare_binara(j+1,n-1,s_laturi);
          counter=counter+pos-j;
      }
    }
    fout<<counter;
    fin.close();
    fout.close();
    return 0;
}