#include<fstream>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");   
int n,i,j,k,s[805],aux,c=0;
int main()
{ 
     f>>n;
     for(i=1;i<=n;i++)
     f>>s[i];
     for(i=1;i<=n;i++)
       for(j=i+1;j<=n;j++)
          if(s[i]>s[j]){aux=s[i];s[i]=s[j];s[j]=aux;} 
     for(i=1;i<=n;i++)
        for(j=i+1;j<=n;j++)
           for(k=j+1;k<=n;k++)
              if(s[i]+s[j]>=s[k])
                c++;
     g<<c;  
     g.close(); 
    return 0;
}