#include<fstream>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int main()
{
    int s[801],i,j,k,n,c=0;
    f>>n;
    for(i=1;i<=n;i++)
    f>>s[i];
    for(i=2;i<=n;i++)
    if(s[i-1]>s[i]) 
    {s[i]=s[i]+s[i-1];
    s[i-1]=s[i]-s[i-1];
    s[i]=s[i]-s[i-1];}
    for(i=1;i<=n-2;i++)
       for(j=i+1;j<=n-1;j++)
          for(k=j+1;k<=n;k++)
             if(s[i]+s[j]>=s[k])
               c++;
    g<<c;
    f.close();
    g.close();
    return 0;
}