Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Name of place | Number of counties | Principal county | Lower zip code |
| --- | --- | --- | --- |
| Yager Junction | 1 | Humboldt County |  |
| Yale | 1 | Riverside County | 92544 |
| Yankee Hill | 1 | Butte County | 95965 |
| Yankee Hill | 1 | Tuolumne County |  |
| Yankee Jims | 1 | Placer County | 95713 |
| Yarmouth | 1 | San Joaquin County |  |
| Yellowjacket | 1 | Tehama County |  |
| Yerba Buena Island | 1 | San Francisco County |  |
| Yermo | 1 | San Bernardino County | 92398 |
| Yettem | 1 | Tulare County | 93670 |
| Ygnacio Valley | 1 | Contra Costa County | 94598 |
| Yokohl | 1 | Tulare County |  |
| Yolano | 1 | Solano County | 95620 |
| Yolo | 1 | Yolo County | 95697 |
| Yontocket | 1 | Del Norte County |  |
| Yorba | 1 | Los Angeles County | 91767 |
| Yorba Linda | 1 | Orange County | 92686 |
| York | 1 | Los Angeles County | 90050 |
| Yorkville | 1 | Mendocino County | 95494 |
| Yosemite Forks | 1 | Madera County |  |
| Yosemite Junction | 1 | Tuolumne County | 95389 |
| Yosemite Lakes | 1 | Madera County |  |
| Yosemite Lakes Park | 1 | Madera County |  |
| Yosemite Lodge | 1 | Mariposa County | 95389 |
| Yosemite National Park | 3 | Madera County | 95389 |
| Yosemite National Park | 3 | Mariposa County | 95389 |
| Yosemite National Park | 3 | Tuolumne County | 95389 |
| Yosemite National Park | 1 | Mariposa County | 95389 |
| Yosemite Valley | 1 | Mariposa County |  |
| Yosemite Village | 1 | Mariposa County |  |
| You Bet | 1 | Nevada County |  |
| Youngstown | 1 | San Joaquin County |  |
| Yountville | 1 | Napa County | 94599 |
| Yreka | 1 | Siskiyou County | 96097 |
| Yreka City | 1 | Siskiyou County | 96097 |
| Yuba City | 1 | Sutter County | 95991 |
| Yuba City Farm Labor Center | 1 | Sutter County | 95991 |
| South Yuba City | 1 | Sutter County | 95991 |
| Yuba Pass | 1 | Nevada County |  |
| Yuba-Sutter Area | 2 | Sutter County Yuba County |  |
| Yucaipa | 1 | San Bernardino County | 92399 |
| Yucca Grove | 1 | San Bernardino County |  |
| Yucca Inn | 1 | San Bernardino County |  |
| Yucca Valley | 1 | San Bernardino County | 92284 |
| Yurok Indian Reservation | 2 | Del Norte County | 95546 |
| Yurok Indian Reservation | 2 | Humboldt County | 95546 |
Question:
how many places have no zip code listed?
Answer:
18