//! ----------------------------------------------
//! Framework <https://github.com/vain0x/procon>
//!
//! See the bottom of file for solution.
//! ----------------------------------------------
#![allow(unused_imports)]
#![allow(non_snake_case)]
use std::cell::RefCell;
use std::cmp::{max, min, Ordering};
use std::collections::*;
use std::fmt::{Debug, Display, Formatter, Write as FmtWrite};
use std::io::{stderr, stdin, BufRead, Write};
use std::mem::{replace, swap};
use std::ops::*;
use std::rc::Rc;
/// Print values to standard error if debug mode.
#[allow(unused_macros)]
macro_rules! debug {
($($e:expr),*) => {
#[cfg(debug_assertions)]
$({
let (e, mut err) = (stringify!($e), stderr());
writeln!(err, "\x1B[33m{}\x1B[0m = {:?}", e, $e).unwrap()
})*
};
}
/// Read from standard input and parse each word.
/// - `read!(T, U, ..)` parses a line as a tuple of words.
/// - `read![[T]]` parses a line as an array of words.
/// - `read![..; N]` parses `N` lines, using `read!(..)` repeatedly.
#[allow(unused_macros)]
macro_rules! read {
([$t:ty] ; $n:expr) =>
((0..$n).map(|_| read!([$t])).collect::<Vec<_>>());
($($t:ty),+ ; $n:expr) =>
((0..$n).map(|_| read!($($t),+)).collect::<Vec<_>>());
([$t:ty]) =>
(rl().split_whitespace().map(|w| w.parse().unwrap()).collect::<Vec<$t>>());
($($t:ty),*) => {{
let buf = rl();
let mut w = buf.split_whitespace();
($(w.next().unwrap().parse::<$t>().unwrap()),*)
}};
}
/// Read a line from standard input.
#[allow(dead_code)]
fn rl() -> String {
let mut buf = String::new();
stdin().read_line(&mut buf).unwrap();
#[allow(deprecated)]
buf.trim_right().to_owned()
}
// -----------------------------------------------
// Solution
// -----------------------------------------------
pub fn lower_bound<T: Ord>(xs: &[T], y: &T) -> usize {
let mut l = 0;
let mut r = xs.len() + 1;
while r - l > 1 {
let m = l + (r - l) / 2;
if &xs[m - 1] < y {
l = m;
} else {
r = m;
}
}
l
}
fn main() {
let N = read!(usize);
let mut L = read![[i64]];
L.sort();
debug!(L);
let mut count = 0;
for a in (0..N).rev() {
for b in (a + 1..N).rev() {
let u = lower_bound(&L, &(L[a] + L[b]));
debug!((a, b, u, L[a], L[b]));
count += u - min(u, b + 1);
}
}
println!("{}", count)
}