说明：  北京大学ACM比赛题目 Write a program to read four lines of upper case (i.e., all CAPITAL LETTERS) text input (no more than 72 characters per line) from the input file and print a vertical histogram that shows how many times each letter (but not blanks, digits, or punctuation) appears in the all-upper-case input. Format your output exactly as shown.
(Peking University ACM Competition Title Write a program to read four lines of upper case (ie, all CAPITAL LETTERS) text input (no more than 72 characters per line) from the input file and print a vertical histogram that shows how many times each letter ( but not blanks, digits, or punctuation) appears in the all-upper-case input. Format your output exactly as shown.)