int led=2;
int tipka=3;
int promjena=LOW;
void setup() {
  // put your setup code here, to run once:
pinMode(led, OUTPUT);
pinMode(tipka, INPUT_PULLUP);
digitalWrite(led, LOW);
}

void loop() {

  // put your main code here, to run repeatedly:
if(digitalRead(tipka)==LOW)
{
  if(promjena==LOW)
  {
    promjena=HIGH;
  }
  else{
    promjena=LOW;
  }
  digitalWrite(led,promjena);
}
}