int led1 = 7;
int led2 = 8;
int led3 = 9;
int led4 = 4;


void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2,OUTPUT);
  pinMode(led3, OUTPUT);
pinMode(led4, OUTPUT);
}

void loop() {
  digitalWrite(led1, HIGH);
  digitalWrite(led2, LOW);
  digitalWrite(led3, LOW);
  digitalWrite(led4, LOW);
delay(1000);

digitalWrite(led1, LOW);
  digitalWrite(led2, HIGH);
  digitalWrite(led3, LOW);
  digitalWrite(led4, LOW);
delay(1000);

digitalWrite(led1, LOW);
  digitalWrite(led2, LOW);
  digitalWrite(led3, HIGH);
  digitalWrite(led4, LOW);
delay(1000);

digitalWrite(led1, LOW);
  digitalWrite(led2, LOW);
  digitalWrite(led3, LOW);
  digitalWrite(led4, HIGH);
delay(1000);
}