// C++ code
//
void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(2, OUTPUT);
  Serial.begin(9600);
}

void loop()
{
    int a[4]; //array of first binary number
    int b[4]; //array of second binary number
    int carry = 0;
    int result[6];

    a[0] = 1;
    a[1] = 0;
    a[2] = 0;
    a[3] = 1;

    b[0] = 1;
    b[1] = 1;
    b[2] = 1;
    b[3] = 1;

    for(int i = 0; i <= 3; i++){
      if(a[i] + b[i] + carry == 0){
          result[i] = 0;
          carry = 0;
      }

      else if(a[i] + b[i] + carry == 1){
          result[i] = 0;
          carry = 0;
      }

      else if(a[i] + b[i] + carry == 2){
          result[i] = 0;
          carry = 1;
      }

      else if(a[i] + b[i] + carry > 2){
          result[i] = 1;
          carry = 1;
      }
    }
    result[4] = carry;
  	if(result[4] == 0){digitalWrite(12, LOW);}
    if(result[4] == 1){digitalWrite(12, HIGH);}
    if(result[3] == 0){digitalWrite(8, LOW);}
    if(result[3] == 1){digitalWrite(8, HIGH);}
    if(result[2] == 0){digitalWrite(7, LOW);}
    if(result[2] == 1){digitalWrite(7, HIGH);}
    if(result[1] == 0){digitalWrite(4, LOW);}
    if(result[1] == 1){digitalWrite(4, HIGH);}
    if(result[0] == 0){digitalWrite(2, LOW);}
    if(result[0] == 1){digitalWrite(2, HIGH);}

    for(int j = 0; j <= 4; j++){
      Serial.println(result[j]); 
    }
    delay(5000);
}