Design a 4-bit decrementer using Half-adders and inverters as building blocks. The circuits impleents A-1=S. Draw the circuit diagram. Hint: consider addtion of the 2s complement of -1 =1111. Begin with a 4-bit adder circuit constructed with 1-bit full adders. The Full Adder blocks constructed with Half- Adder blocks and OR gates can be simplified to a single Half Adder black and inverters considering the special second argument (1111). OR gates can be eliminated