int led1 = 2; 
int led2 = 3;
int led3 = 4;
int led4 = 5;
void setup() {
     pinMode(led1,OUTPUT);
     pinMode(led2,OUTPUT);
     pinMode(led3,OUTPUT);
     pinMode(led4,OUTPUT);
}
void loop() {
    digitalWrite(led1,HIGH);
    delay(100);
        digitalWrite(led1,LOW);
    digitalWrite(led2,HIGH);
    delay(100);
    digitalWrite(led2,LOW);
    digitalWrite(led3,HIGH);
    delay(100);
    digitalWrite(led3,LOW);
    digitalWrite(led4,HIGH);
    delay(100);
    digitalWrite(led4,LOW);
    delay(200);
}