#include<fstream.h>
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int v[1000],i,j,e,n,s;
int main()
{
in>>n;
for(i=1; i<=n; i++)
	in>>v[n];


for(i=1; i<n-1; i++)
	for(j=i+1; j<n; j++)
		for(e=j+1; e<=n; e++)
			if(v[i]+v[j]>v[e] && v[j]+v[e]>v[i] && v[i]+v[e]>v[j])
				s++;


out<<s;



out<<'\n';
return 0;
}