void setup() {
  Serial.begin(9600);
  Serial.println("Introduction to Microprocessor");
  Serial.println("Enter The Operation");
  Serial.println("For example: 1+1");
}

void loop() {
  if (Serial.available() > 0) {
    String input = Serial.readStringUntil('\n');
    float n1, n2;
    char op;

    int opi = input.indexOf('+');
    if (opi == -1) opi = input.indexOf('-');
    if (opi == -1) opi = input.indexOf('*');
    if (opi == -1) opi = input.indexOf('/');

    if (opi != -1) {
      n1 = input.substring(0, opi).toFloat();
      n2 = input.substring(opi + 1).toFloat();
      op = input.charAt(opi);

      Serial.print("Entered Operation: ");
      Serial.println(input);

      float result;
      bool operation = true;

      switch (op) {
        case '+':
          result = n1 + n2;
          break;
        case '-':
          result = n1 - n2;
          break;
        case '*':
          result = n1 * n2;
          break;
        case '/':
          if (n2 != 0) {
            result = n1 / n2;
          } else {
            Serial.println("Error");
            operation = false;
          }
          break;
      }

      if (operation) {
        Serial.print("Result: ");
        Serial.println(result);
      }
    } else {
      Serial.println("Error");
    }

    Serial.println("Enter Operation:");
  }
}