public int a(int i) {
        int j = this.c(i);

        // Changes start
        int shift = shift(i);
        int aval = this.a[j];
        return (aval >> shift) & 15;
        // Changes end
    }

    public void a(int i, int j) {
        int k = this.c(i);
        
        // Changes start
        int shift = shift(i);
        int aval = this.a[k];
        aval &= ~(15<<shift);
        aval |= (j & 15) << shift;
        this.a[k] = (byte) aval; // Note: Using long[] would increase performance even more.
        // Changes end
    }

    // Changes start
    private int shift(int i) {
    	return (i & 1) >> 2;
    }
    // Changes end