Permission denied to execute function

Question

I am trying to run the code given below, where "myApp" is function Name in the Script which one I am trying to run.

ExecutionRequest request = new ExecutionRequest().setFunction("myApp").setDevMode(true);
try {
    Operation op = service.scripts().run("some id", request).execute();
    // Print results of request.
    if (op.getError() != null) {
        // The API executed, but the script returned an error.
        System.out.println("Error");
    } else {
        System.out.println("Success");
    }
} catch (GoogleJsonResponseException e) {
    e.printStackTrace(System.out);
}

Its giveing error me like:

{ "code" : 404, "errors" : [ { "domain" : "global", "message" : "Requested entity was not found.", "reason" : "notFound" } ], "message" : "Requested entity was not found.", "status" : "NOT_FOUND" }

or if I am deploying this as a web app it's giving this type of error:

com.google.api.client.googleapis.json.GoogleJsonResponseException: 403 Forbidden { "code" : 403, "errors" : [ { "domain" : "global", "message" : "The caller does not have permission", "reason" : "forbidden" } ], "message" : "The caller does not have permission", "status" : "PERMISSION_DENIED" }

What I have to do run the code perfectly????