function var bool: all_different(array[int] of var int: x) =
	let {
		set of int: S = range(1, length(x));
	} in forall([
		int_neq(element(x, i),element(x, j))
		| i in S,
			j in S 
			where int_lt(i,j)
	]);

function bool: main(int: n) =
	let {
		array[1..n] of var 1..n-1: pigeon;
		constraint all_different(pigeon);
	} in true;