#include<cstdio>
#include<algorithm>
int v[801];
int main()
{
 freopen("nrtri.in","r",stdin);
 freopen("nrtri.out","w",stdout);
 int n;
 scanf("%d ",&n);
 for(int i=1;i<=n;i++)
     scanf("%d ",&v[i]);
 std::sort(v+1,v+n+1);
 int rasp=0;
 for(int i=1;i<=n-2;i++)
     for(int j=i+1;j<=n-1;j++)
         {
          int sq=j+1;
          while(v[i]+v[j]>=v[sq] && sq<=n)
                sq++,rasp++;
         }
 printf("%d\n",rasp);
 return 0;
}