def fib_iter(n):
<EOL>assert n >= <NUM_LIT:0>, '<STR_LIT>'<EOL>fib_1 = <NUM_LIT:0><EOL>fib_2 = <NUM_LIT:1><EOL>sum = <NUM_LIT:0><EOL>if n <= <NUM_LIT:1>:<EOL><INDENT>return n<EOL><DEDENT>for _ in range(n-<NUM_LIT:1>):<EOL><INDENT>sum = fib_1 + fib_2<EOL>fib_1 = fib_2<EOL>fib_2 = sum<EOL><DEDENT>return sum<EOL>
[summary]
    Works iterative approximate O(n)

    Arguments:
        n {[int]} -- [description]

    Returns:
        [int] -- [description]