void setup() {
 pinMode(7, OUTPUT);
 pinMode(6, OUTPUT);
 pinMode(5, OUTPUT);
 pinMode(4, OUTPUT);
 pinMode(3, OUTPUT);
}
int speed=300;
int count=1;
void loop() {
  
  digitalWrite(7,HIGH);
  delay(speed);
  digitalWrite(7,LOW);
  delay(speed);
  digitalWrite(6,HIGH);
  delay(speed);
  digitalWrite(6,LOW);
  delay(speed);
  digitalWrite(5,HIGH);
  delay(speed);
  digitalWrite(5,LOW);
  delay(speed);
  digitalWrite(4,HIGH);
  delay(speed);
  digitalWrite(4,LOW);
  delay(speed);
  digitalWrite(3,HIGH);
  delay(speed);
  digitalWrite(3,LOW);
  delay(speed);
  count++;
  if(count==2){
    speed-=100;
  }else   if(count==3){
    speed-=100;
  }else   if(count==4){
    speed-=50;
  }
}