#include <fstream>
#include <algorithm>
using namespace std;

ifstream is("nrtri.in");
ofstream os("nrtri.out");

int n, a[801], nrtri;

int main()
{
    is >> n;
    for ( int i = 0; i < n; i++ )
        is >> a[i];
    for( int i = 0; i < n - 2; i++ )
        for( int j = i + 1; j < n - 1; j++ )
            for( int k = j + 1; k < n; k++ )
                if( a[i] <= a[j] + a[k] && a[j] <= a[i] + a[k] && a[k] <= a[i] + a[j] )
                    nrtri++;
    os << nrtri;
    is.close();
    os.close();
    return 0;
}