/* ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) ) ( ( ) */ #include <bits/stdc++.h> #define fore(i, a, b) for (signed i = (a), i##_last = (b); i < i##_last; ++i) #define fort(i, a, b) for (signed i = (a), i##_last = (b); i <= i##_last; ++i) #define ford(i, a, b) for (signed i = (a), i##_last = (b); i >= i##_last; --i) #define fi first #define se second #define pb push_back #define sz(x) ((int)(x).size()) #define all(x) (x).begin(), (x).end() #define rall(x) (x).rbegin(), (x).rend() using namespace std; using ll = long long; using ld = long double; template<class A, class B> bool maxi(A &a, const B &b) {return (a < b) ? (a = b, true):false;}; template<class A, class B> bool mini(A &a, const B &b) {return (a > b) ? (a = b, true):false;}; typedef unsigned long long ull; typedef pair<int, int> ii; typedef vector<ll> vi; typedef vector<ii> vii; typedef vector<vi> vvi; typedef vector<vii> vvii; const int maxN = 5005; int n, h[270], suffix[3][maxN]; string s, t; int main() { bool flag; #ifdef LOCAL freopen("input.INP", "r", stdin); #endif // LOCAL cin.tie(0) -> sync_with_stdio(0); cout.tie(0); cin >> n >> s >> t; for (const char &c : s) ++h[c - 'a']; ford(i, n - 1, 0) { fore(j, 0, 3) suffix[j][i] = suffix[j][i + 1]; ++suffix[t[i] - 'a'][i]; } fore(i, 0, n) fore(c, 0, 3) { if (c + 'a' == t[i] || h[c] <= 0) continue; --h[c]; flag = true; for (int x = 0, y, z; x < 3 && flag; ++x) for (y = x + 1; y < 3 && flag; ++y) { z = 3 - x - y; if (h[x] + h[y] < suffix[z][i + 1]) flag = false; } if (flag) { cout << (char)(c + 'a'); break; } else ++h[c]; } cout << '\n'; return 0; }