#include<iostream>
#include<fstream>
using namespace std;
int main ()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    int i,n,a,b,v[800],ok,c=0,x,pos,aux,j,k;
    f>>n;
    for(i=1;i<=n;i++)
    {
        f>>v[i];
    }
    do
    {
        ok=1;
        for(i=1;i<=n-1;i++)
        {
            if(v[i]>v[i+1])
            {
                ok=0;
                aux=v[i];
                v[i]=v[i+1];
                v[i+1]=aux;
            }
        }
    } while(ok!=1);
    for(i=1;i<=n-2;i++)
    {
        for(j=i+1;j<=n-1;j++)
        {
           for(k=j+1;k<=n;k++)
           {
               if(v[k]<=v[i]+v[j])
               {
                   c++;
               }
           }
        }
    }
    g<<c;
    return 0;

}