use proconio::input;

fn main(){
  input!{
    n:usize,
    mut reward:[usize;n * 3],
  }

  let mut amount = [0;10];
  for i in reward{
    match i {
      1 => amount[0] += 1,
      2 => amount[1] += 1,
      3 => amount[2] += 1,
      4 => amount[3] += 1,
      5 => amount[4] += 1,
      6 => amount[5] += 1,
      7 => amount[6] += 1,
      8 => amount[7] += 1,
      9 => amount[8] += 1,
      10 => amount[9] += 1,
      _ => {},
    }
  }
  let mut level = 0;
  for i in 0..9{
    while amount[i] >= 2{
      amount[i] -= 2;
      level += 1;
    }
  }
  let rest:usize = amount.iter().sum();
  level += rest / 4;

  println!("{}",level);
}