int l1=10,l2=9,l3=8,l4=7;
void setup() {
  // put your setup code here, to run once:
pinMode(l1, OUTPUT);
pinMode(l2, OUTPUT);
pinMode(l3, OUTPUT);
pinMode(l4, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(l1, LOW);
digitalWrite(l2, LOW);
digitalWrite(l3, LOW);
digitalWrite(l4, HIGH);
if(l1==HIGH)
{
   digitalWrite(l2, LOW);
   digitalWrite(l3, LOW);
   digitalWrite(l4, LOW);
}
if(l2==HIGH)
{
  digitalWrite(l1, LOW);
  digitalWrite(l3, LOW);
  digitalWrite(l4, LOW);
}
if(l3==HIGH)
{
  digitalWrite(l1, LOW);
  digitalWrite(l2, LOW);
   digitalWrite(l4, LOW);
}
else{
   digitalWrite(l1, LOW);
digitalWrite(l2, LOW);
digitalWrite(l3, LOW);

}
}