#include <iostream>
#include <fstream>
#include <iomanip>
#include <cmath>
#include <string>

using namespace std;

int main(){
    ifstream in("desifravimas-vyr.in");
    ofstream out("desifravimas-vyr.out");
    int N,K;
    char x;
    in>>N;                              //1
    char A[N]={ },B[N]={ };
    for(int i=0;i<N;i++)                //2n
    {
        in>>x;
        A[i]=x;
    }
    for(int i=0;i<N;i++)                //2n
    {
        in>>x;
        B[i]=x;
    }
    int o=0;
    while(A[o]==B[o])                   //n
        o++;
    K=int(A[o])-int(B[o]);
    for(int i=0;i<N;i++)                //7n^3
    {                                       //↖↖
        if(int(B[i])>64&&int(B[i])<91)          //3n^2
        {                                         //↖↖
            if(int(B[i])+K>90)                      //n
                out<<char(int(B[i])+K-26);
            else if(int(B[i])+K<65)                 //n
                out<<char(int(B[i])+K+26);
            else                                    //n
                out<<char(int(B[i])+K);
        }
        else if(int(B[i])>96&&int(B[i])<123)
        {
            if(int(B[i])+K>122)
                out<<char(int(B[i])+K-26);
            else if(int(B[i])+K<97)
                out<<char(int(B[i])+K+26);
            else
                out<<char(int(B[i])+K);
        }
        else
            out<<B[i];
    }
    return 0;
}

//is viso 7n^3+5n+1