Electric charges depending on values of N+ electric signals and values of corresponding positive loads are held in first capture-and-storage circuitry. Electric charges having a size depending on values of (N−N+) electric signals and corresponding absolute values of negative loads are held in second capture-and-storage circuitry. A sum of N+ multiplied values obtained by multiplying each of the positive loads by each of the values of the N+ electric signals is calculated when a voltage held in the first capture-and-storage circuitry reaches a first threshold. A sum of (N−N+) multiplied values obtained by multiplying each of the absolute values by each of the values of the (N−N+) electric signals is calculated when a voltage held in the second capture-and-storage circuitry reaches a second threshold A sum of N multiplied values is obtained by subtracting the sum of (N−N+) multiplied values from the sum of N+ multiplied values.