#include <fstream>
#include <algorithm>
using namespace std;
int v[801];

int main()
{
    ifstream in("nrtri.in");
    ofstream out("nrtri.out");
    int n,i,j,nr=0,k;
    in>>n;
    for(i=1;i<=n;i++) in>>v[i];
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
    {
        for(j=i+1;j<=n-1;j++)
        {
            k=j+1;
            while(v[i]+v[j]>=v[k] && k<=n)
            {
                nr++;
                k++;
            }
        }
    }
    out<<nr;
    return 0;
}