#include <cstdio>
#include <algorithm>
using namespace std;

#define MAXN 805

int main(){

  freopen("nrtri.in", "r", stdin);
  freopen("nrtri.out", "w", stdout);

  int N, A[MAXN], i, j, res;

  scanf("%d", &N);
  for(i=0; i<N; i++)
    scanf("%d", A+i);

  sort(A, A+N);

  res=0;
  for(i=0; i<N; i++)
    for(j=i+1; j<N; j++)
      res+=upper_bound(A+j+1, A+N, A[i]+A[j])-A-j-1;
  
  printf("%d\n", res);

  return 0;

}