PROBLEM TO BE SOLVED: To improve convenience of an operator.SOLUTION: An acquisition section 11 acquires a character string 2 recognized from an image 1, accuracy indicating accuracy of recognition about each character included in the character string 2, and a character string 3 inputted according to an input operation. A determination section 12 compares each character included in the character string 2 with each character included in the character string 3 from the head of the character string on a one-to-one basis, and extracts a first character "2" when the compared characters are different from each other and the accuracy corresponding to the first character "2" is a first threshold or larger from the character string 2. The determination section 12 also extracts a second character "3" which is adjacent to the first character "2" and of which corresponding accuracy is less than a second threshold from the character string 2. The determination section 12 determines that a pair of characters "32" of the ch
