How to get all values corresponding to a key in json having duplicate key-value members?

Question

I am using jsoncpp to work on a JSON with duplicate key-pair values. My JSON is something like:

dict = {
    "a" : "1",
    "b" : "2",
    "c" : "3",
    "a" : "4",
    "c" : "5"
}

Even though this JSON looks 'invalid', I want to get a list of values (1,4) when dict["a"] is accessed. How to get this?