void setup() {
  volatile char *dirf, *dirk;
  dirf = 0x30;
  *dirf = 0x03;
  dirk = 0x107;
  *dirk = 0x03;
}

void loop() {
  volatile char *outf, *outk; //both the ports are output port
  volatile long i;
  outf = 0x31;
  outk = 0x108;;
  *outk = 0x00;
  *outf = 0x01;  //LED 2,4
  for (i = 0; i < 500000; i++);
  *outk = 0x00;
  *outf = 0x02; //LED 1,3
  for (i = 0; i < 500000; i++);

}