#include <fstream>
#include <algorithm>

using namespace std;

ifstream in("nrtri.in");
ofstream out("nrtri.out");

int n, v[801], cnt;
int pas, indice, nr_format;

int main(){
	in >> n;

	for (int i = 1; i <= n; ++ i)
		in >> v[i];


	sort(v, v + n + 1);


	for (int i = 1; i <= n - 2; ++ i){
		for (int j = i + 1; j <= n - 1; ++ j){

      pas = 1;
      pas = pas << 32 - __builtin_clz(n) - 1;
      nr_format = 0;

      for (pas; pas > 0; pas = pas >> 1){
      	indice = nr_format + pas;

      	if (indice <= n && v[indice] <= v[i] + v[j] && v[i] <= v[indice] + v[j] && v[j] <= v[indice] + v[i])
      		nr_format += pas;
      }

      if (nr_format <= j)
      	continue;
      else{
      	cnt += nr_format - j;
      }

		}
	}

	out << cnt;

	return 0;
}