#include <iostream>
#include <string>
using namespace std;

int main()
{
    int key;
    string s;
    cin >> key >> s;
    for (int i = 0; i < s.size(); i++)
    {
        if (s[i] == 'z')
        {
            s[i] = 'a';
            s[i] += (key - 1);
        }
        s[i] += key;
    }
    cout << s;
}