byte pinOnArr[4] = {9, 7, 5, 3};
byte pinOffArr[4] = {8, 6, 4, 2};
const byte relayPin = 13;
byte relayState, wasPress;
void setup()
{
  for (int i = 0; i < 4; i++)
  {
    pinMode(pinOnArr[i], INPUT_PULLUP);
    pinMode(pinOffArr[i], INPUT_PULLUP);
  }
  pinMode(relayPin, OUTPUT);
}

void loop()
{
  switch (relayState){
    case 0:
      for (int i = 0; i < 4; i++) {
        if (!digitalRead(pinOnArr[i])){
          digitalWrite(relayPin, true);
          relayState = 1;
          wasPress = i;
          return;
        }
      }
    break;
    case 1:
      if (!digitalRead(pinOffArr[wasPress])){
         digitalWrite(relayPin, false);
         relayState = 0;
      }
    break;
  }
  delay(50);
}