#![allow(non_snake_case)]
#![allow(unused_imports)]
#![allow(unused_macros)]
#![allow(clippy::needless_range_loop)]
#![allow(clippy::comparison_chain)]
#![allow(clippy::nonminimal_bool)]
#![allow(clippy::neg_multiply)]
#![allow(dead_code)]
// use itertools::Itertools;
// use std::collections::{BTreeSet, HashSet, VecDeque};
// use std::f64::consts::PI;
use proconio::fastout;
use proconio::*;
// use std::cmp::{max, min};
/*
インタラクティブ
macro_rules! input(($($tt:tt)*) => (
    let stdin = std::io::stdin();
    let mut stdin = proconio::source::line::LineSource::new(std::io::BufReader::new(stdin));
    proconio::input!(from &mut stdin, $($tt)*);
));
*/

#[fastout]
fn main() {
    input! {
        n: usize,
        a: [usize; n],
    }
    let mut countList: Vec<Vec<usize>> = vec![vec![0; 2001]; n];
    for i in (0..n).rev() {
        for j in 0..2001 {
            if i < n - 1 {
                countList[i][j] = countList[i + 1][j];
            }
        }
        countList[i][a[i]] += 1;
    }

    let mut ans = 0;
    for i in 0..n {
        for j in i + 1..n {
            if (a[j] as i128) - (a[i] as i128) - 10 <= 0 {
                continue;
            }
            let diff = a[j] - a[i] - 10;
            for k in j + 1..n {
                if (a[k] == a[j] - diff) && (a[k] + diff + 1 < 2001) {
                    ans += countList[k][a[k] + diff + 1];
                }
            }
        }
    }
    println!("{}", ans);
}