#include <bits/stdc++.h>   using namespace std;   int main() {     size_t n;     string s, t;     cin >> n >> s >> t;     int base = ( z  -  a ) + 1;     vector<int> l(n + 1), r(n + 1);     for (int i = 0; i < int(n); ++i) {       l[i + 1] = s[i] -  a ;     }     for (int i = 0; i < int(n); ++i) {       r[i + 1] = t[i] -  a ;     }     for (int i = n; i >= 0; --i) {       l[i] += r[i];       if (i > 0) {         l[i - 1] += l[i] / 26;         l[i] %= 26;       }     }     vector<int> res(n + 1);     for (int i = 0; i <= n; ++i) {       int rem = l[i] % 2;       l[i] /= 2;       if (i < n) {         l[i + 1] += rem * 26;       }     }     for (int i = 1; i <= n; ++i) {       cout << char(l[i] +  a );     }     cout << endl;     return 0;   }   