import std.algorithm, std.array, std.range;
import std.string, std.conv;
import std.stdio, std.typecons;

void main()
{
  auto n = readln.chomp.to!int;
  auto abci = iota(n).map!(i => readln.split.map!(to!int).map!(i => i - 1));

  auto items = [0,0,0,0,0,0,0,0,0,0];
  foreach (abc; abci) {
    foreach (i; abc) {
      items[i] += 1;
    }
  }

  auto r = 0;
  foreach (ref item; items) {
    r += item / 2;
    item %= 2;
  }

  writeln(r + count!("a == 1")(items) / 4);
}