7. The computer program product of claim 6 , wherein the converted character string is generated by appending the at least one character, which is common to a predetermined reference number or more of parts in the second text, to the target character string.
6. The computer program product of claim 1 , further comprising retrieving the target character string from a second text which is different from the first text and generates the converted character string by appending at least one character, which is located in at least either one of the previous and subsequent positions of the retrieved target character string, to the target character string.