void setup() 
{
  pinMode(1, OUTPUT);
  pinMode(2,OUTPUT);
}

void loop() 
{
 digitalWrite(1, HIGH);
 digitalWrite(2, LOW);
 delay(1000);// Wait for 1000 millisecond(s)
 digitalWrite(1, LOW);
 digitalWrite(2, HIGH);
 delay(1000);// Wait for 1000 millisecond(s)
}