int s = 0;

void setup()
{
    pinMode(13, OUTPUT);
}

void loop()
{
  if(digitalRead(2)==LOW) {
    s=s+1;
    if(s>2)
     s=0;
    delay(20);
    while(digitalRead(2)==LOW) {}
  }
  if (s==0) {
    digitalWrite(13, LOW);
  }
  if (s==1) {
    digitalWrite(13, HIGH);
  }
  if (s==2) {
    digitalWrite(13, HIGH);
    delay(100);
    digitalWrite(13, LOW);
    delay(100);
  }
}