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 |
| --- | --- | --- | --- |
| Abbott | 1 | Scott County | 72944 |
| Abco | 1 | Hot Spring County |  |
| Aberdeen | 1 | Monroe County | 72134 |
| Acorn | 1 | Polk County | 71953 |
| Ada | 1 | Conway County | 72001 |
| Adams Field | 1 | Pulaski County | 72202 |
| Adona | 1 | Perry County | 72001 |
| Advance | 1 | Baxter County |  |
| Aetna | 1 | Craighead County |  |
| Aggie | 1 | Craighead County |  |
| Agnos | 1 | Fulton County | 72513 |
| Agricultural School | 1 | Columbia County |  |
| Air Base | 1 | Pulaski County | 72076 |
| Airport Village | 1 | Jackson County |  |
| Alabam | 1 | Madison County | 72740 |
| Alamo | 1 | Montgomery County |  |
| Albert | 1 | Montgomery County |  |
| Albert Pike | 1 | Garland County | 71913 |
| Albion | 1 | White County | 72143 |
| Alco | 1 | Stone County | 72610 |
| Alexander | 1 | Greene County | 72450 |
| Alexander | 2 | Pulaski County | 72002 |
| Alexander | 2 | Saline County | 72002 |
| Alf | 1 | Montgomery County |  |
| Alfrey | 1 | Monroe County | 72021 |
| Algoa | 1 | Jackson County | 72112 |
| Alicia | 1 | Lawrence County | 72410 |
| Alix | 1 | Franklin County | 72820 |
| Allbrook | 1 | Howard County | 71851 |
| Alleene | 1 | Little River County | 71820 |
| Allendale | 1 | Monroe County |  |
| Allene | 1 | Little River County |  |
| Allfriend | 1 | Newton County | 72664 |
| Allis | 1 | Drew County |  |
| Allison | 1 | Stone County | 72511 |
| Allport | 1 | Lonoke County | 72046 |
| Alma | 1 | Crawford County | 72921 |
| Almond | 1 | Cleburne County | 72550 |
| Almyra | 1 | Arkansas County | 72003 |
| Alpena | 2 | Boone County | 72611 |
| Alpena | 2 | Carroll County | 72611 |
| Alpha | 1 | Yell County |  |
| Alpine | 1 | Clark County | 71920 |
| Alread | 1 | Van Buren County | 72031 |
| Altheimer | 1 | Jefferson County | 72004 |
| Alto | 1 | Poinsett County | 72354 |
| Altus | 1 | Franklin County | 72821 |
| Aly | 1 | Yell County | 72857 |
| Amagon | 1 | Jackson County | 72005 |
| Amanca | 1 | Crittenden County | 72376 |
| Amboy | 1 | Pulaski County |  |
| Ames | 1 | Nevada County |  |
| Amity | 1 | Clark County | 71920 |
| Amy | 1 | Ouachita County | 71701 |
| Anderson | 1 | Scott County |  |
| Anderson Tully | 1 | Poinsett County |  |
| Andrews | 1 | White County |  |
| Annieville | 1 | Lawrence County | 72434 |
| Anthony | 1 | Hempstead County | 71801 |
| Anthony Subdivision | 1 | Crittenden County |  |
| Anthonyville | 1 | Crittenden County | 72301 |
| Antioch | 1 | Craighead County |  |
| Antioch | 1 | Hot Spring County |  |
| Antioch | 1 | Perry County | 72070 |
| Antioch | 1 | White County | 72012 |
| Antoine | 1 | Pike County | 71922 |
| Apalco | 1 | Lafayette County |  |
| Apex | 1 | Sebastian County | 72938 |
| Aplin | 1 | Perry County | 72126 |
| Appleby | 1 | Washington County |  |
| Applegate Ford | 1 | Carroll County |  |
| Appleton | 1 | Pope County | 72822 |
| Apt | 1 | Craighead County | 72403 |
| Arbaugh | 1 | Newton County | 72852 |
| Arbor Grove | 1 | Lawrence County | 72433 |
| Arcadia | 1 | Hempstead County | 71857 |
| Ard | 1 | Yell County | 72834 |
| Arden | 1 | Little River County | 71822 |
| Arkadelphia | 1 | Clark County | 71923 |
| Arkalite | 1 | Lonoke County |  |
| Arkana | 1 | Baxter County |  |
| Arkana | 1 | Lafayette County | 71826 |
| Arkansas A and M College | 1 | Drew County |  |
| Arkansas City | 1 | Desha County | 71630 |
| Arkansas Fuel Oil Company Village | 1 | Columbia County | 71753 |
| Arkansas Polytechnic College | 1 | Pope County |  |
| Arkansas Post National Memorial | 1 | Arkansas County | 72055 |
| Arkansas State Teachers College | 1 | Faulkner County |  |
| Arkawana | 1 | Baxter County |  |
| Arkinda | 1 | Little River County | 71836 |
| Arkola | 1 | Sebastian County | 72945 |
| Arlberg | 1 | Stone County |  |
| Armorel | 1 | Mississippi County | 72310 |
| Armstrong | 1 | Sharp County | 72482 |
| Armstrong Springs | 1 | White County | 72148 |
| Arnett | 1 | Washington County |  |
| Artesian | 1 | Calhoun County |  |
| Artex | 1 | Miller County |  |
| Arthur | 1 | Conway County | 72156 |
| Artist Point | 1 | Crawford County |  |
| Ashdown | 1 | Little River County | 71822 |
| Asher | 1 | Madison County | 72727 |
| Asher | 1 | Pulaski County | 72204 |
| Ash Flat | 2 | Sharp County | 72513 |
| Ash Flat | 2 | Fulton County | 72513 |
| Ashton | 1 | Chicot County | 71653 |
| Athelstan | 1 | Mississippi County | 72370 |
| Athens | 1 | Howard County | 71971 |
| Atkins | 1 | Pope County | 72823 |
| Atlanta | 1 | Columbia County | 71740 |
| Attica | 1 | Randolph County | 72455 |
| Atwood | 1 | Howard County |  |
| Aubrey | 1 | Lee County | 72311 |
| Augsburg | 1 | Pope County | 72874 |
| Augusta | 1 | Woodruff County | 72006 |
| Aurelle | 1 | Union County | 71765 |
| Aurora | 1 | Madison County | 72740 |
| Austin | 1 | Conway County | 72027 |
| Austin | 1 | Lonoke County | 72007 |
| Austin Station | 1 | Lonoke County |  |
| Auvergne | 1 | Jackson County | 72112 |
| Avant | 1 | Garland County |  |
| Avery | 1 | Lincoln County | 71639 |
| Avilla | 1 | Saline County | 72002 |
| Avoca | 1 | Benton County | 72711 |
| Avon | 1 | Sevier County | 71832 |
| Azor | 1 | Nevada County | 71835 |
Question:
which city name has the least number of unique letters?
Answer:
Ada