#include <stdio.h>   
#include <algorithm>   
  
using namespace std;   
  
int v[801],i,j,n,nr,k,ok=0;   
  
int main()   
{   
    freopen("nrtri.in","r",stdin);   
           
    scanf("%d", &n);   
    for (i=0;i<n;++i)   
         scanf("%d", &v[i]);   
    sort(v,v+n);   
    for (i=0;i<n-2;++i)          
    for (j=i+1;j<n-1;++j)         
    for (k=j+1;k<=n;++k)         
        if (v[k]<=v[i]+v[j] && v[j]<=v[k]+v[i] && v[i]<=v[k]+v[j]) nr++;     
        else break;    
    freopen("nrtri.out","w",stdout);   
    printf("%d",nr);   
return 0;   
}