题解

#include<iostream>
#include<string>
using namespace std;
int main(){
    int n,m;
    string s;
    cin>>n>>m>>s;
    for(int i=0;i<s.size();i++){
        s[i]='a'+(s[i]-'a'-m%26+26)%26;
    }
    cout<<s;
    return 0;
}