Question: What is the population of the city where KPSZ is located?

full_context: Document 1: KXIC: KXIC (800 AM) is a radio station licensed to serve Iowa City, Iowa and the greater Johnson County area. The station is owned by iHeartMedia, Inc. and licensed to Citicasters Licenses, Inc. It airs a News/Talk radio format.
Document 2: Des Moines, Iowa: On September 22, 1851, Des Moines was incorporated as a city; the charter was approved by voters on October 18. In 1857, the name ``Fort Des Moines ''was shortened to`` Des Moines'', and it was designated as the second state capital, previously at Iowa City. Growth was slow during the Civil War period, but the city exploded in size and importance after a railroad link was completed in 1866.
Document 3: KIPR: KIPR (92.3 FM, "Power 92 Jams") is a commercial radio station carrying an urban contemporary format located in Little Rock, Arkansas and licensed to Pine Bluff. It is owned by Cumulus Media. The station's studios are located in West Little Rock, and the transmitter tower is located in Jefferson, south of Pine Bluff. Due to the transmitter location emitting 100 kilowatts, the signal covers most of Central Arkansas including places like Brinkley, North Little Rock, Gould, Fordyce and Dumas.
Document 4: KPSZ: KPSZ (940 AM, "Praise 940") is a Christian radio station serving the Des Moines, Iowa, area. The station's studios are located on Locust Street in Des Moines along with Saga Communications' other Des Moines stations (KRNT, KSTZ, KIOA, KMYR and KAZR), while its 8-tower transmitter array is located near Hartford.
Document 5: Des Moines, Iowa: Age spread: 24.8% under the age of 18, 10.6% from 18 to 24, 31.8% from 25 to 44, 20.4% from 45 to 64, and 12.4% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 93.8 males. For every 100 females age 18 and over, there were 90.5 males.
Document 6: Middletown, Iowa: Middletown is a city in Des Moines County, Iowa, United States. The population was 318 at the 2010 census. It is part of the Burlington, IA–IL Micropolitan Statistical Area.
Document 7: Saylorville, Iowa: Saylorville is a census-designated place (CDP) in Polk County, Iowa, United States. The population was 3,301 at the 2010 census. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area. The Saydel Community School District is located in this area. The unincorporated community of Marquisville is in this area.
Document 8: Cedar Rapids, Iowa: As of the 2010 United States Census, the city population was 126,326. The estimated population of the three - county Metropolitan Statistical Area, which includes the nearby cities of Marion and Hiawatha, was 255,452 in 2008. Cedar Rapids is an economic hub of the state, located in the core of the Interstate 380.
Document 9: Des Moines metropolitan area: The Des Moines metropolitan area, officially known as the Des Moines -- West Des Moines, IA Metropolitan Statistical Area (MSA), consists of five counties in central Iowa, United States: Polk, Dallas, Warren, Madison, and Guthrie. The 2010 census population of these counties was 569,633, and the 2017 estimated population was 645,911.
Document 10: KDPS: KDPS is a radio station in Des Moines, Iowa. The station is owned by Des Moines Public Schools. The school district programs the station during daytime hours with a variety of rock music styles and staffs it with high school students who are learning radio. Most evenings and on weekends, KDPS is programmed by Grand View University with alternative rock music on weeknights and children's music on weekends, however every Friday is called Hip Hop Friday, as they play hip hop the entire day.
Document 11: Johnston, Iowa: Johnston is a city in Polk County, Iowa, United States. The population was 17,278 in the 2010 census, an increase of almost 100% from the 8,649 population in the 2000 census. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area.
Document 12: KESZ: KESZ (99.9 FM; "KEZ") is an adult contemporary radio station based in Phoenix, Arizona. The station is owned and operated by iHeartMedia. Its studios are located in Phoenix near Sky Harbor Airport and its transmitter is in South Mountain Park.
Document 13: KSTZ: KSTZ (102.5 FM, "Star 102.5") is a commercial FM radio station in Des Moines, Iowa. The station has a Hot Adult Contemporary radio format. KSTZ is part of Saga Communications' Des Moines Radio Group, along with KPSZ, KRNT, KAZR, KIOA, and KMYR, with studios located on Locust Street in Des Moines.
Document 14: KJJQ: KJJQ's transmitter is located in the town of Volga, South Dakota, but the studios are in the nearby city of Brookings. Known as The Ranch AM 910, the station has a broad range transmitting across eastern South Dakota and western Minnesota, reaching the cities of Yankton, South Dakota, Webster, South Dakota, Chamberlain, South Dakota, Marshall, Minnesota, Olivia, Minnesota, and the communities between these points. The station was formerly in a historic train depot and went by the name "Depot Radio". In 2005, the depot was sold and KJJQ relocated to the building now housing the other four commercial radio stations in Brookings.
Document 15: Indianola, Iowa: Indianola is a city in Warren County, Iowa, United States, 18 miles south of Des Moines, Iowa. The population was 14,782 at the 2010 census. It is the county seat of Warren County.
ground_truth: 645,911
sub_queries: What city is KPSZ located? Answer: Des Moines
what is the population of the Des Moines area Answer: 645,911