Need help writing a simple formula for a calculated column

I have a choice column named "City" with three choices:
1. Los Angeles
2. Houston
3. Denver

I have a calculated column named "State" and want it to display a string based on the following condtions:
1. If City is "Los Angeles" then display "CA"
2. If City is "Houston" then display "TX"
3. If City is "Denver" then display "CO"

This is what I have so far but the syntax is incorrect:
=IF([City]="Los Angeles", CA), IF([City]="Houston", TX), IF([City]="Denver", CO)