int a = 0;
void setup() {
  for(int led = 7; led <= 12; led++)
  pinMode(led, OUTPUT);
  pinMode(2, INPUT);
  Serial.begin(9600);
}

void loop() {
  Serial.println(a);
  if(digitalRead(2) == 1){
    while(digitalRead(2) == 1);
    a++;
  }
  if(a == 1){
    for(int i = 7; i <= 12; i++)
      digitalWrite(i, HIGH);
  }
  if(a == 2){
    for(int i = 7; i <= 12; i++)
      digitalWrite(i, LOW);
  }
  if(a == 3) a = 1;
}