int A=5;
int B=4;
int C=2;
void setup() {
  pinMode(A, OUTPUT);
  pinMode(B, OUTPUT);
  pinMode(C, OUTPUT);
}
void loop() {
digitalWrite(A, HIGH);
delay(100);
digitalWrite(A, LOW);
delay(100);
digitalWrite(B, HIGH);
delay(100);
digitalWrite(B, LOW);
delay(100);
digitalWrite(C, HIGH);
delay(100);
digitalWrite(C, LOW);
delay(100);
}