Json deserialize?

I'm practicing with ArduinoJson library. I have created this simple example, where I serialize (put tohgeter into a Json object) two numbers.

In the second part of the code i would like to extract from this serialized object the elements inside this object and print them individually, how can I do this?

this is the code:

#include <ArduinoJson.h>

String Js;
int a;
int b;

void setup() {
  Serial.begin(9600);
}

void loop() {
  //Sensor Reading (Adafruit)


  a = 10 + random(1,5);
  b = 30 - random(1,5);

delay(1000);
  
    DynamicJsonDocument doc(100); 
    doc["Random_Numb_a"] = a;
    //long Number_b = doc["Random_Numb_b"] = b;
    serializeJson(doc,Js);
    Serial.println(Js);



Serial.println("Deserialization part");
StaticJsonDocument<100> DeSerial;
 //deserialization
deserializeJson(DeSerial,Js);

 //Serial.println(DeSerial);
 Serial.println(DeSerial["Random_Numb_a"]);
}

I solved this way:

#include <ArduinoJson.h>

String Js;
int a;
int b;
int i;

void setup() {
  Serial.begin(9600);
}

void loop() {

 String Js;            
 Js = "";              //reinizializziamo Js, altrimenti continua ad immagazzinare dati, senza questo comando.

 i = i + 1;

  a = 10 + random(1,5);
  b = 30 - random(1,5);

  Serial.println("Serialization Part: (Object Js) ");
    
    //StaticJsonDocument <100> doc;  //2  Stack Mem
    DynamicJsonDocument doc(100);  //1  Heap Mem
    doc["Random_Numb_a"] = a;
    doc["Random_Numb_b"] = b;

    serializeJson(doc,Js);
    Serial.print("from Js:  ");
    Serial.println(Js);
    Serial.println("");

    
    delay(4000);
    Serial.println("Deserialization part: (Object DeSerial) ");
    DynamicJsonDocument DeSerial(100);
     //deserialization
    DeserializationError err = deserializeJson(DeSerial,Js);
    long Num_a = DeSerial["Random_Numb_a"];
    long Num_b = DeSerial["Random_Numb_b"];
    
      Serial.print("from DeSerial --> Num_a:  ");
      Serial.println(Num_a);
      Serial.print("from DeSerial --> Num_b:  ");
      Serial.println(Num_b);
      Serial.println("");
    delay(4000);
}