macro_rules! input {
    ($($r:tt)*) => {
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(std::io::stdin()));
        let mut next = move |is_word: bool| -> String{
            if is_word {
                bytes
                    .by_ref()
                    .map(|r|r.unwrap() as char)
                    .skip_while(|c|c.is_whitespace())
                    .take_while(|c|!c.is_whitespace())
                    .collect()
            } else {
                bytes
                    .by_ref()
                    .map(|r|r.unwrap() as char)
                    .skip_while(|c| c == &'\n')
                    .take_while(|c| c != &'\n')
                    .collect()
            }
        };
        input_inner!{next, $($r)*};
    };
}
macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, static $var:ident : $t:tt $($rest:tt)*) => {
        $var = read_value!($next, $t);
        input_inner!{$next $($rest)*}
    };

    ($next:expr, mut $var:ident : $t:tt $($rest:tt)*) => {
        let mut $var = read_value!($next, $t);
        input_inner!{$next $($rest)*}
    };

    ($next:expr, $var:ident : $t:tt $($rest:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($rest)*}
    };
}
macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; all ]) => { {
            let mut str = $next(false);
            str.split_whitespace().map(|it| it.parse::<$t>().unwrap()).collect::<Vec<_>>()
        }
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len as usize).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, lines) => {
        {
            let mut vec = Vec::new();
            let mut str = $next(false);
            while str != "" {
                vec.push(str);
                str = $next(false);
            }
            vec
        }
    };

    ($next:expr, line) => {
        $next(false)
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next(true).parse::<$t>().expect("Parse error")
    };
}

pub fn get_time() -> f64 {
    static mut STIME: f64 = -1.0;
    let t = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).unwrap();
    let ms = t.as_secs() as f64 + t.subsec_nanos() as f64 * 1e-9;
    unsafe {
        if STIME < 0.0 {
            STIME = ms;
        }
        ms - STIME
    }
}

fn main() {
    input! {
        n: usize,
        mut a : [isize; n]
    }

    let mut a13 = Vec::new();
    let mut a24 = Vec::new();

    for i in 0..n {
        for j in (i + 1)..n {
            if a[i] == a[j] - 10 {
                a13.push((i, j));
            }
            if a[i] == a[j] - 1 {
                a24.push((i, j));
            }
        }
    }

    let mut ans = 0;

    for &(a1, a3) in &a13 {
        for &(a2, a4) in &a24 {
            if a1 < a2 && a2 < a3 && a3 < a4 && a[a1] + 10 < a[a2] {
                ans += 1;
            }
        }
    }

    println!("{}", ans);

}