#include<fstream> 
#include<algorithm> 
using namespace std;  
int v[999],n,i,q,k,j,aux; 
int main()  
{      
	ifstream fin("nrtri.in"); 
    fin>>n;   
	for(i=1;i<=n;i++)          fin>>v[i];    
	for(i=1;i<=n-1;i++)
	{
		for(j=i+1;i<=n;j++)
			{if(v[i]>=v[j]){aux=v[i];v[i]=v[j];v[j]=aux;}   
			}
	}
	for(i=1;i<n-1;i++)          for(j=i+1;j<n;j++)              for(k=j+1;k<=n;k++)                  if(v[i]+v[j]>=v[k])                      q++;                  else break;    
	ofstream fout("nrtri.out");  
	fout<<q;  return 0;  }