#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int n,i,j,p,a[803],s,nr;
int main()
{
    fin >> n ;
    for(i = 1 ;i <= n;i ++)fin>>a [ i ];
    sort ( a+1, a + n + 1);
    for( i=1;i <=n - 2;i++)
    {
                for(p =i+1;p<= n - 1;p++)
                {
                            s=a[i]+a[p];
                            for(j= p+1;j<=n&&s>=a[j] ;j++)nr++;
                }
    }
    fout << nr <<'\n';

    return 0;
}