#include<fstream> 
using namespace std; 
int n,i,j,aux,nr,k,a[801]; 
int main() 
{ 
ifstream f("nrtri.in"); 
ofstream g("nrtri.out"); 
f>>n; 
for(i=1;i<=n;i++) 
f>>a[i]; 
for(i=1;i<=n-1;i++) 
for(j=i+1;j<=n;j++) 
if(a[i]>a[j]) 
{ 
aux=a[i]; 
a[i]=a[j]; 
a[j]=aux; 
} 
for(i=1;i<=n;i++) 
for(j=i+1;j<=n;j++) 
for(k=j+1;k<=n;k++) 
if(a[i]+a[j]>=a[k]) 
nr++; 
g<<nr; 
return 0; 
}