Letters Cyclic Shift
题目描述
You are given a non-empty string s consisting of lowercase English letters. You have to pick exactly one non-empty substring of s and shift all its letters 'z' 
'y' 'x' 
'b' 'a' 'z'. In other words, each character is replaced with the previous character of English alphabet and 'a' is replaced with 'z'.
What is the lexicographically minimum string that can be obtained from s by performing this shift exactly once?
The only line of the input contains the string s (1≤|s|≤100000) consisting of lowercase English letters.
Print the lexicographically minimum string that can be obtained from s by shifting letters of exactly one non-empty substring.
codeforces
bncdenqbdr
abacaba
aaacaba
String s is lexicographically smaller than some other string t of the same length if there exists some 1≤i≤|s|, such that s1=t1,s2=t2,...,si-1=ti-1, and si<ti.
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