#include <iostream>
using namespace std;
int n;
string a;
int main(){
	cin >>n;
	cin >>a;
	for(int i=0;i<a.size();i++){
		if(a[i]>'z'){
			cout <<"a";
		}else{
			a[i]=a[i]+n;
			if(a[i]>'z'){
				cout <<"a";
                break;
			}else{
				cout <<a[i];
			}
		}		
	}
	return 0;
}