#include <fstream.h>
int main()
{ int i,j,l,n,v[801],k=0;
ifstream f ("nrtri.in");
ofstream g ("nrtri.out");
f>>n;
for (i=1;i<=n;i++) f>>v[i];
for (i=1;i<=n-2;i++) 
	for (j=i+1;j<=n-1;j++)
		for (l=j+1;l<=n;l++) 
			if (v[i]+v[j]>=v[l] && v[j]+v[l]>=v[i] && v[l]+v[i]>=v[j]) k++;
g<<k;
f.close();
g.close();
return 0;
}