#include <fstream>

using namespace std;
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int n,v[800],ok;
int main()
{
    fin>>n;
int i,j,aux;
for(i=1;i<=n;i++)
    fin>>v[i];
    for(i=1;i<n;i++)
        for(j=i+1;j<=n;j++)
            if(v[i]>v[j])
        {
            aux=v[i];
            v[i]=v[j];
            v[j]=aux;
        }
int a,b,c;
for(a=1;a<=n-2;a++)
    for(b=a+1;b<=n-1;b++)
    for(c=b+1;c<=n;c++)
    if(v[a]+v[b]>=v[c])
        ok++;
    fout<<ok;
    return 0;
}