const byte led1 = 6;
const byte led2 = 7;
const byte led3 = 5;

void setup() {
  pinMode (led1,OUTPUT);
  pinMode (led2,OUTPUT);
  pinMode (led3,OUTPUT);

}
void loop() {
digitalWrite(led1, HIGH);
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
delay(15000);
digitalWrite(led1, LOW);
digitalWrite(led2, HIGH);
digitalWrite(led3, LOW);
delay(10000);
digitalWrite(led1, LOW);
digitalWrite(led2, LOW);
digitalWrite(led3, HIGH);
delay(5000);
}