int zustand = 0;
void setup() {
  Serial.begin(9600); //9600 bits/sek -> baud
  pinMode(4,OUTPUT);
  pinMode(15,OUTPUT);
  pinMode(25,INPUT);
  pinMode(26,INPUT);
}

void loop() {
  int taster1 = digitalRead(25);
  int taster2 = digitalRead(26);
  Serial.print("Taster 1: ");
  Serial.print(taster1);
  Serial.print("     Taster 2: ");
  Serial.println(taster2);
  if(taster1 == 0||taster2==1){
   if(zustand == 0){
     digitalWrite(4,HIGH);
     digitalWrite(15,HIGH);
     zustand = 1;
   }else{
     digitalWrite(4,LOW);
     digitalWrite(15,LOW);
     zustand = 0;
   }
  }
   delay(100);
}