#include<fstream>
using namespace std; 
ifstream f("nrtri.in");
ofstream g("nrtri.out");

int i, n, a[805],aux,j,k,con=0;
int main()
{

f>>n;
for(i=1;i<=n;i++)
f>>a[i];
for(i=1;i<=n;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])
con++;

g<<con;
g.close();
return  0;
}