#include<cstdio>  
#include<algorithm> 
using namespace std;   
int a[1024], n;   
int main(){   
  FILE *in, *out;
  in=freopen("nrtri.in", "r", stdin);
  out=freopen("nrtri.out", "w", stdout);
  int i, nrtri=0;   
  scanf("%d", &n);   
  for(i=0;i<n;i++)   
    scanf("%d", &a[i]);   
  sort(a, a+n);   
  int j, k;   
  for(i=0;i<n-2;i++)   
    for(j=i+1;j<n-1;j++)   
      for(k=j+1; k<n; k++)   
    if( a[i]+a[j]>=a[k] )   
      nrtri++;   
  printf("%d\n",nrtri);
  return 0;   
}