#include<bits/stdc++.h>
#include<cstring> 
using namespace std;
char str[51];
int main(){
	int a ;
	cin >> a;
	cin >> str;
	for (int i = 0;;i ++){
        if (str[i] != '\0'){
    		if (str[i] == 'z'){
    			cout << "a";
    		}
    		else{
    			 str[i] += a; 
    			 cout << char(str[i]); 	
    		}
}
        else {
            break;
}
}
    return 0;
}