It's not that we add up no matter how many columns. I mean, in the txt file in the compressed package I uploaded, there are all three forms, namely ten-digit, hundred-digit, thousand-digit. The 10th line in a txt file may be ten-digit, or hundred-digit, or thousand-digit, but there is always a number, and the position of this number is basically fixed. I found that the last digit (units digit) of the numbers in several txt files is always in a fixed character position.
For example, in 1.txt, the 10th line is 123; in 2.txt, the 10th line is 1234; in 3.txt, the 10th line is 34. The positions of the units digits 3, 4, 4 above should be aligned.
Thank you for your enthusiastic help!!! :P