#include <stdio.h>
#include <stdlib.h>
int e[804];
int compar(const void * a,const void * b)
{
	 return ( *(int*)a - *(int*)b );

}
int main()
{
	int a,n,i,j,d=0,l;
	FILE *f1,*f2;
	f1=fopen("nrtri.in","r");
	f2=fopen("nrtri.out","w");
	fscanf(f1,"%d",&n);
	for(i=1;i<=n;i++)
		fscanf(f1,"%d",&e[i]);
	

	qsort(e,n+1,sizeof(int),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;
				}
		}
	}

	fprintf(f2,"%d",d);

	return 0;
}