void loop() {
timerStart = analogRead(startR);
timerStart = map(timerStart, 0, 1023, 0, 3000);
timerStart = constrain(timerStart, 0, 3000);

timerFinish = analogRead(finishR);
timerFinish = map(timerFinish, 0, 1023, 0, 3000);
timerFinish = constrain(timerFinish, 0, 3000);

  if (digitalRead(isSig) == LOW) {
   Serial.println("Button pressed");
    digitalWrite(gas, HIGH);

        if (millis() - timer1 >= timerStart) {
             digitalWrite(dr, HIGH);
             digitalWrite(st, HIGH);
               timer1 = millis();
            }

 } else{
  digitalWrite(dr, LOW);
  digitalWrite(st, LOW);
         if (millis() - timer2 >= timerFinish) {
          digitalWrite(gas, LOW);
               timer2 = millis();
            }
  }
 }