import java.math.BigInteger;

class BigNatural {
    private BigInteger value;  /* invariant: value >= 0 */

    public BigNatural() {
	value = new BigInteger("0");
    }

    public BigNatural(int init) {
	value = new BigInteger(String.valueOf(init));
    }

    public BigNatural(BigNatural b) {
	value = new BigInteger(b.toString());
    }

    public String toString() {
	return value.toString();
    }

    public void increment() {
	value = value.add(BigInteger.ONE);
    }

    public void decrement() {
	if (!value.equals(BigInteger.ZERO)) {
	    value = value.subtract(BigInteger.ONE);
	}
    }

}