#include<fstream>
using namespace std;
#define max 801


int main()
{
    ifstream fin ( "ntri.in") ;
    ofstream fout ( "ntri.out" ) ;
    long  i,j,k,n,rez;
    fin >> n;
    long a[max];
    rez=0;
    
    for(i = 1;i<=n;i++)
        fin >> a[i];
    
    for(i = 1;i<=n-2;++i)
        for(j = i+1;j<=n-1;++j)
            for(k = j+1;k<=n;++k)
            {
                if(a[i] + a[k] >= a[j] && a[i] + a[j] >= a[k] && a[k] + a[j] >= a[i]){
                    rez++;
                }
            }
    
    fout << rez;
    
    return 0;
}