const int ledone = 7;
const int ledtow = 8;
const int ledthr = 9;

void setup() {
  pinMode(ledone, OUTPUT);
  pinMode(ledtow, OUTPUT);
  pinMode(ledthr, OUTPUT);
}

void loop() {
  digitalWrite(ledone, HIGH);
  delay(1000);
  digitalWrite(ledone, LOW);
  digitalWrite(ledtow, HIGH);
  delay(1000);
  digitalWrite(ledtow, LOW);
  digitalWrite(ledthr, HIGH);
  delay(1000);
  digitalWrite(ledthr, LOW);
}