Fibonacci function

HAI 1.3
    HOW IZ I FIBUN YR NUM
        BOTH SAEM NUM AN 0, O RLY?
            YA RLY
                FOUND YR 0
            MEBBE BOTH SAEM NUM AN 1
                FOUND YR 1
            NO WAI
                FOUND YR SUM OF I IZ FIBUN YR DIFF OF NUM AN 1 MKAY AN I IZ FIBUN YR DIFF OF NUM AN 2 MKAY
        OIC
    IF U SAY SO
KTHXBYE