int led1 = 7;int led2 = 6;int led3 = 5;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);
}

