#include<cstdio>
#include<algorithm>

#define MAX_SIZE 805

FILE *f=fopen("nrtri.in","r");
FILE *g=fopen("nrtri.out","w");

using namespace std;

int N,v[MAX_SIZE];
long long result;

void read (  void )
{
    fscanf(f,"%d",&N);
    for(int i(1); i <= N ; fscanf(f,"%d",&v[i++]) );
    fclose(f);
}
void solve( void )
{
    sort(v+1,v+N+1);
  for(int i(1); i < N ; ++i )
      for(int j(i+1); j< N ; ++j)
    result+=(long long)(upper_bound(v+j+1,v+N+1,v[i]+v[j])-(v+j+1));
}
void write( void )
{

    fprintf(g,"%lld",result);
    fclose(g);

}
int main( void )
{
    read();
    solve();
    write();
    return 0;
}