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