macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let mut s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};

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

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };

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

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

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

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

fn eratosthenes_linear(n: usize) -> (Vec<usize>, Vec<bool>) {
    if n < 2 {
        return (Vec::new(), Vec::new());
    }
    let mut is_prime = vec![true; n + 1];
    let mut prime_list = Vec::new();
    let mut min_factor = vec![0; n + 1];
    is_prime[0] = false;
    is_prime[1] = false;
    for i in 2..=n {
        if is_prime[i] {
            prime_list.push(i);
            min_factor[i] = i;
        }
        for &j in &prime_list {
            if i * j > n || j > min_factor[i] {
                break;
            }
            is_prime[i * j] = false;
            min_factor[i * j] = j;
        }
    }
    (prime_list, is_prime)
}

fn main() {
    input! {
        n: usize,
    }
    let (primes, is_prime) = eratosthenes_linear(n);
    let mut ans = 0;
    for &r in &primes {
        let p = r * r - 2;
        if p <= n && is_prime[p] {
            ans += if p == 2 { 1 } else { 2 };
        }
    }
    println!("{}", ans);
}