String inputmsg;
int condition1 = 55;

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

void loop()
{
delay(250); //Estää serialin floodauksen

if (Serial.available() > 0 && (inputmsg == condition1))
  {
  String inputmsg = Serial.readStringUntil('\n');
  Serial.println("Correct input");
  }
    else if (Serial.available() > 0 && (inputmsg != condition1))
     {
     String inputmsg = Serial.readStringUntil('\n');
    Serial.println("Incorrect input");
     }

Serial.println(inputmsg); //tulostaa input msg arvon.
}