# let list1 = [1; 2; 3];;
val list1 : int list = [1; 2; 3]
# let list2 = [4; 5; 6];;
val list2 : int list = [4; 5; 6]
# let list1and2 = list1 @ list2;;
val list1and2 : int list = [1; 2; 3; 4; 5; 6]