I have a dynamically changing json array and I need to reference the array length using jmespath query. For example

{
  "locations": [
    {"name": "Seattle", "state": "WA"},
    {"name": "New York", "state": "NY"},
    {"name": "Bellevue", "state": "WA"},
    {"name": "Olympia", "state": "WA"}
  ]
}

If I use jmespath query like length(locations), I get the desired result 4

and if I use locations[0], I get desired result { “name”: “Seattle”, “state”: “WA” }

but lets say I want to combine both the queries like locations[length(locations)] which should translate to locations[4] but this does not work at all. I tried many combinations to get the array length but this is not working. Can anyone help me here?
I need this because my json array length changes dynamically based on user interaction