#include <stdio.h>
int v[805],n;

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);
	
	for (i=0; i<n-2; i++)
		for (j=i+1; j<n-1; j++)
			for (k=j+1; k<n; k++)
				if ((v[i]+v[j]>=v[k])&&(v[j]+v[k]>=v[i])&&(v[i]+v[k]>=v[j]))
					nrtri++;
	
	FILE *out=fopen("nrtri.out","w");
	fprintf(out,"%d\n",nrtri);
	fclose(out);
	
	return 0;
}