#include <fstream>
#include <algorithm>
using namespace std;
 int v[801],n,i,j,k,s;

int main()
{
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    fin>>n;
    for (i=1;i<=n;i++)
        f>>v[i];
     sort(v+1,v+n+1);
     for (i=1;i<=n;i++)
        for (j=i+1;j<=n-1;j++)
            for(k=j+1;k<=n;k++)
                if (v[i]+v[j]>=v[k]) s++;
                    else break;
    fout<<s;
}