void setup() 
{
    pinMode(7, OUTPUT);
    pinMode(8, OUTPUT);
    pinMode(12, OUTPUT);
    digitalWrite(7, LOW);
    digitalWrite(8, LOW);
    digitalWrite(12, LOW);
}
void loop()
{
    digitalWrite(12, HIGH);
    digitalWrite(8, LOW);
    digitalWrite(7, LOW);
    delay(1000);
    digitalWrite(12, LOW);
    digitalWrite(8, HIGH);
    digitalWrite(7, LOW);
    delay(1000);
    digitalWrite(12, LOW);
    digitalWrite(8, LOW);
    digitalWrite(7, HIGH);
    delay(1000);
}