import strutils, sequtils, math
var
  stock: array[10, int]
  cnt = 0
let N = stdin.readLine.parseInt

for i in 0 ..< N:
  let t = stdin.readLine.split.map parseInt
  for t in t: stock[t - 1] += 1

for i in 0 ..< stock.len:
  while stock[i] >= 2:
    stock[i] -= 2
    cnt += 1

cnt += stock.sum div 4
echo cnt