Solution when you do not know how many times python input() should be done

Quoted by SO:

Use file.read.

input_str=sys.stdin.read()
https://stackoverflow.com/questions/21235855/how-to-read-user-input-until-eof/36237166

You may want to create a file for input and pass it over to the redirect to verify its operation.

Many programming contests, including AtCoder, allow you to determine the number of lines of input.For example:

x_{11}y_{11}
x_{12}y_{12}
x_{13}y_{13}

x_{21}y_{21}
x_{22}y_{22}

This concludes the entry.Do you see that the last x_{22}y_{22} corresponds to x_{NA_{N}}y_{NA_{N}}?