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