#include<fstream.h> 
int n,i,j,x[801],l,aux,nr;
ifstream fin("nrtri.in");    
ofstream fout("nrtri.out");  
int main() 
{     
	   
	fin>>n;     
	for(i=1;i<=n;i++) 
		fin>>x[i];     
	for(i=1;i<=n-1;i++) 	
		for(j=i+1;j<=n;j++) 
			if(x[i]>x[j]) 
			{ 
				aux=x[i]; 
			    x[i]=x[j]; 
			    x[j]=aux;
			} 
	for(i=1;i<=n;i++)		
		for(j=i+1;j<=n;j++) 
			for(l=j+1;l<=n;l++) 
			 if(x[i]+x[j]>=x[l]) nr++;    
    fout<<nr;   					
return 0;
}