boolean fbut = 0;
boolean fled = 1;
int pins[] = {4, 5, 18, 19, 21};
int i = 0;

void setup() {
  pinMode(15, INPUT_PULLUP);
  pinMode(pins[0], OUTPUT);
  pinMode(pins[1], OUTPUT);
  pinMode(pins[2], OUTPUT);
  pinMode(pins[3], OUTPUT);
  pinMode(pins[4], OUTPUT);
  Serial.begin(9600);
}

void loop() {
  boolean but = !digitalRead(15);

  if (but == 1 & fbut == 0) {
    fbut = !fbut;
    digitalWrite(pins[i], fled);
    i += 1;
    Serial.println("pressed");
    delay(500);
  }

  if (but == 0 & fbut == 1) {
    fbut = !fbut;
    Serial.println("no");
  }

  if (i > 4) {
    i = 0;
    fled = !fled;
  }
}