#include <stdio.h>
int main()
{
	int n,d=0,i,j,l;
	int e[805];
	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]);
	}
	for(i=1;i<=n;i++)
	{
				for(j=i+1;j<=n;j++)
				{
						for(l=j+1;l<=n;l++)
						{
							if(e[l]<=e[j]+e[i] && e[j]<=e[l]+e[i] && e[i]<=e[l]+e[j])
							d++;
						}
				}
	}
	
	fprintf(f2,"%d",d);
	fclose(f1);
	fclose(f2);
	return 0;
}