void setup() {
  pinMode(0, OUTPUT); // Set pin '0' OUTPUT 
  pinMode(3, INPUT); // Set pin '3' INPUT
}

void loop() {
  int painike = digitalRead(3); 
// Read pin 3 state put value on painike
  if (painike == HIGH) { // if painike High do this
    digitalWrite(0, HIGH); // Led on
  } else if (painike == LOW) { // if painike == Low do that
    digitalWrite(0, LOW); // Led off
  }
}