#include <stdio.h>
#include <stdlib.h>

int v[805],n;

int comp(const void *a, const void *b)
{
	int *aa=(int*) a, *bb=(int*) b;
	int x=*aa, y=*bb;
	if (x<y)
		return 1;
	if (x>y)
		return -1;
	return 0;
}


int main()
{
	int nrtri=0,i,j,k;
	
	FILE *in=fopen("nrtri.in","r");
	
	fscanf(in,"%d",&n);
	for (i=0; i<n; i++)
		fscanf(in,"%d",&v[i]);
	fclose(in);
	qsort(v,n,sizeof(v[0]),comp);
	
	for (i=0; i<n-2; i++)
		for (j=i+1; j<n-1; j++)
		{
			k=j+1;
			while (v[i]+v[j]>=v[k])
			{
				if ((v[i]+v[j]>=v[k])&&(v[j]+v[k]>=v[i])&&(v[i]+v[k]>=v[j]))
					nrtri++;
				k++;
			}
		}
	
	FILE *out=fopen("nrtri.out","w");
	fprintf(out,"%d\n",nrtri);
	fclose(out);
	
	return 0;
}