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

int main()
{
    int a;
    string b;
    cin>>a>>b;
    for(int i=0;i<b.length();i++)
    {
        if(b[i]=='z')b[i]='a'+a-1;
        else b[i]=b[i]+a;
    }
    for(int i=0;i<b.length();i++)cout<<b[i];
    return 0;
}