Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

Example Input: Yellow fever begins suddenly after an incubation period of three to ____ days.
Example Output: five

Example Input: Narwhals have ____ teeth in their upper jaw.
Example Output: two

Example Input: Individuals typically inherit ____ alleles for each gene.
Example Output:
two