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