: LEAVE R> R> DROP I 1- >R >R ;

: ROLL
    DUP NOT IF EXIT THEN
    1+ DUP PICK          ( n val )
    SWAP 2 * (roll)      ( val )
    SWAP DROP
;

: 2OVER 3 PICK 3 PICK ;
: 2SWAP 3 ROLL 3 ROLL ;