#include <fstream.h>
#include <stdlib.h>
int e[1001];
int compar(const void * a,const void * b)
{return ( *(int*)a - *(int*)b );}
int main()
{int a,n,i,j,d=0,l;
ifstream q("nrtri.in");
ofstream w("nrtri.out");
q>>n;
for(i=1;i<=n;i++)
  q>>e[i];
qsort(e,n+1,sizeof(e[0]),compar);
for(i=1;i<=n;i++)
  for(l=i+1;l<=n;l++)
    for(j=n;j>=l+1;j--)
	  if(e[j]<=e[i]+e[l])
	   {d=d+(j-l);
	   break;}
w<<d;
return 0;}