// C++ code
int led1=1;
int led2=2;
int led3=3;
int led4=4;
int sw1=5;
int sw2=6;
int i=0;
void setup()
{
  pinMode(led1,OUTPUT);
  pinMode(led2,OUTPUT);
  pinMode(led3,OUTPUT);
  pinMode(led4,OUTPUT);
  pinMode(sw1,INPUT);
  pinMode(sw2,INPUT);	
}

void loop()
{
  if(digitalRead(sw1)==HIGH)
  {
    i++;
  }
  if(digitalRead(sw2)==HIGH)
  {
    if(i>0)
    {
      i--;
    }
  }
    switch(i)
    {
      case 1 :{digitalWrite(led1,HIGH);
               digitalWrite(led2,LOW);
               digitalWrite(led3,LOW);
               digitalWrite(led4,LOW);
               break;}
      case 2 :{digitalWrite(led2,HIGH);
               digitalWrite(led1,LOW);
               digitalWrite(led3,LOW);
               digitalWrite(led4,LOW);
               break;}
      case 3 :{digitalWrite(led3,HIGH);
               digitalWrite(led1,LOW);
               digitalWrite(led2,LOW);
               digitalWrite(led4,LOW);
               break;}
      case 4 :{digitalWrite(led4,HIGH);
               digitalWrite(led1,LOW);
               digitalWrite(led2,LOW);
               digitalWrite(led3,LOW);
               break;}
      default :{
                 i=0;
                 break;
      }
    }
   
  delay(200);
}