(* ------------------ First Version ------------------ *)
(* Check to see if the two inputs are relatively prime
 * Return 1 if they are relative prime, otherwise return 0 *)
let is_prime x y =
    let ret = ref 1 in
    let i = ref 2 in
    let cond = min x y in
        while (!i <= cond) do
            if (((x mod !i) = 0) && ((y mod !i) = 0)) then
                (ret := 0; i:= x + 1)
            else
                i := !i + 1
        done;
        !ret


(* ------------------ Second Version ------------------ *)        
(* Using Euclidean algorithm to determine 
 * the greatest common divisor (GCD) of
 * two elements of any integers *)        
let gcd x y = 
    let a = ref x in
    let b = ref y in
    let c = ref 0 in
    while (!b <> 0) do 
        c := !a;
        a := !b;
        b := !c mod !b
    done;
    !a
  
(* Check to see if the two inputs are relatively prime
 * Return 1 if they are relative prime, otherwise return 0 *)
let is_prime_super x y = 
    if (gcd x y == 1) then 1 else 0

        
(* Return the number of positive numbers <= n
 * that are relatively prime to n *)
let euler n = 
    let ret = ref 1 in
    for i = 2 to (abs n)-1 do
        ret := !ret + (is_prime_super i (abs n))
    done;
    !ret