#define LED1 4
#define LED2 5
#define LED3 6
#define LED4 7
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(2, INPUT_PULLUP);
pinMode(LED1, OUTPUT);
pinMode(LED2, OUTPUT);
pinMode(LED3, OUTPUT);
pinMode(LED4, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
int a, b, SW1;
SW1 = digitalRead(2);
SW1 = SW1+1;
//b=a<<1;
Serial.println(SW1);
delay(500);
switch(SW1)
    {
      case 0 : turnon(LED1);delay(500);turnoff(LED1);
        break;
      case 1 : turnon(LED2);delay(500);turnoff(LED2);
        break;
      case 2 : turnon(LED3);delay(500);turnoff(LED3);
        break;
      case 3 : turnoff(LED4); delay(500);turnoff(LED4);
        break;
      default : Serial.println("Invalid");
        break;
    }
}
void turnon(byte led)
   { 
   digitalWrite(led , HIGH);
   }
void turnoff(byte led)
 { 
  digitalWrite(led , LOW);
  }