#include<fstream.h>
int main(){
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");
int N;
long int a[800];
fin>>N;
for (short i=0;i<N;i++)
    fin>>a[i];
short ok=0;
int p=N;
long long S=0;
while (ok==0){
   ok=1;
   p--;
   for (int i=0;i<N;i++)
       if (a[i]>a[i+1]){
	   long int aux=a[i];
	   a[i]=a[i+1];
	   a[i+1]=aux;
	   ok=0;}   }
long int P=0;
int f=0;
for (int j=0;j<N-2;j++){
   P=a[j]+a[j+1];
    for (f=j+2;f<N;f++)
	if (P<a[f])
	   break;
   S+=f-j-2;               }
fout<<S;
fin.close();
fout.close();
return 0;}