int period = 10;
unsigned long time_now = 0;
int period1 = 10;
unsigned long time_now1 = 0;
int period2 = 10;
unsigned long time_now2 = 0;
int period3 = 10;
unsigned long time_now3 = 0;
 
void setup() {
    Serial.begin(9600);
}
 
void loop() {
    unsigned long currentMillis = millis();
    if ((currentMillis - time_now) > period){
        time_now = millis();
        Serial.println("1");
    }
    unsigned long currrntMillis = millis();
    if ((currentMillis - time_now1) > period1){
        time_now1 = millis(); 
        Serial.println("2");
        }
    if(millis() >= time_now2 + period2){
        time_now2 += period2;
        Serial.println("3");
    }
    if(millis() >= time_now3 + period3){
        time_now3 += period3;
        Serial.println("4");
    }
   
    //Run other code
}