use std::collections::HashMap;

use proconio::{input, marker::Chars};

fn main() {
    input! {
        a: [i32],
    };
    let mut cnt: HashMap<i32, i32> = HashMap::new();
    a.iter().for_each(|ai| {
        cnt.entry(*ai)
            .and_modify(|counter| *counter += 1)
            .or_insert(1);
    });
    let ans: i32 = cnt.values().map(|x| x / 2).sum();
    println!("{}", ans);
}