public class L0476_NumberComplement {
    // 
    public int findComplement(int num) {
        // 
        int mask = num;
        mask |= mask >> 1;
        mask |= mask >> 2;
        mask |= mask >> 4;
        mask |= mask >> 8;
        mask |= mask >> 16;
        
        // 
        return num ^ mask;
    }
    
    //  highestOneBit
    public int findComplementV2(int num) {
        // 
        int highestBit = Integer.highestOneBit(num);
        // (highestBit >= 1;
            mask