#include<fstream>  
 using namespace std;  
 int main()  
 {  
     ifstream in("nrtri.in");  
     ofstream out("nrtri.out");  
     int n,x,j,k,l,v[801],w,i;  
     in>>n;  
     for(i=1;i<=n;i++)  
     {  
         in>>x;  
         v[i]=x;  
     }  
     w=0;  
     for(j=1;j<=n;j++)  
         for(k=j+1;k<=n;k++)  
             for(l=k+1;l<=n;l++)  
                 if ((v[j]+v[k]>=v[l])&&(v[j]+v[l]>=v[k])&&(v[l]+v[k]>=v[j])) w++;  
     out<<w;  
     in.close();  
     out.close();  
     return 0;  
 }