#include<fstream>
using namespace std;
int v[801],n;
int partition(int p,int r)
{int x=v[r];
int i=p-1;
for(int j=p;j<r;j++) {if(v[j]<x) {i++;int aux=v[j];v[j]=v[i];v[i]=aux;}}
  int aux2=v[r];v[r]=v[i+1];v[i+1]=aux2;
  return i+1;   
     }
void quicksort(int p,int q)
 {if(p<q)
  {int m=partition(p,q);
   quicksort(p,m-1);
   quicksort(m+1,q);
         
         }
     
     }     
int cautare(int p, int u,int i,int j)
{
  int m;
  m=(p+u)/2;
  while (p<=u){
      if ((v[m]<=v[i]+v[j] && v[m+1]>v[i]+v[j]) || (v[m]<=v[i]+v[j] && m==n-1))
		  return m;
	  else if (v[m]<=v[i]+v[j] && v[m+1]<=v[i]+v[j]) {
		  p=m+1; 
		  m=(p+u)/2;
	  }
	  else {
		  u=m-1; 
		  m=(p+u)/2;
		  }  
  }
  return 0;
}
int main()
{freopen("nrtri.in","r",stdin);
freopen("nrtri.out","w",stdout);
scanf("%d",&n);

int rez=0;
for(int i=0;i<n;i++) scanf("%d",&v[i]);
quicksort(0,n-1);

for(int i=0;i<=n-1;i++)
 for(int j=i+1;j<=n-2;j++)
  {int r=cautare(0,n,i,j);
   
    if(r>=j && r!=0) rez+=r-j;
         
         }    
printf("%d",rez);  
  return 0;       
    }