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