programming language is java.

In Eve's mailbox service, each PO box is labeled with a letter followed by an integer. Given integers numRows and numColumns,

output the label for each PO box, followed by a space. End each row with a newline.

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Note:

Rows are in alphabetical order. PO boxes in the first row all start with the letter A$.$

Columns are in ascending order. PO boxes in the first column all end with the integer $1.$

Add an empty string at the beginning of the output to properly concatenate characters and integers.