1. A method of mapping a logical expression to a logic circuit, the expression comprising a first and a second product term including n and m logic functions, wherein m is greater than n, the method comprising: placing a first multiple-input logic gate having at least n input terminals and an output terminal; connecting the input terminals of the first multiple-input logic gate to directly input the logic functions of the first product term so that the first product term is output from the output terminal of the first multiple-input logic gate; placing a second multiple-input logic gate having less than m input terminals and an output terminal, and an unit multiplexer having a first input terminal, a second input terminal to input a constant, a control terminal and an output terminal; connecting the first input and control terminal of the unit multiplexer to input at least two of the logic functions of the second product term; and connecting the input terminals of the second multiple-input logic gate to input the logic functions of the second product term by inputting the at least two of the logic functions through the output terminal of the unit multiplexer so that the second product term is output from the output terminal of the second multiple-input logic gate.