#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;
	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(j=n;j>=i+2;j--)
		{
			if(e[j]<=e[i]+e[i+1])
			{
				d=d+(j-1-i);
				break;
			}
		}
	}

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

	return 0;
}