#include <bits/stdc++.h>
using namespace std;
#define int long long
mt19937_64 rng(std::chrono::system_clock::now().time_since_epoch().count());
std::string longestCommonSubsequence(const std::string& X, const std::string& Y) {
    int m = X.size();
    int n = Y.size();
    std::vector<std::vector<int>> dp(m+1, std::vector<int>(n+1, 0));

    // Fill dp table
    for (int i = 1; i <= m; i++) {
        for (int j = 1; j <= n; j++) {
            if (X[i-1] == Y[j-1])
                dp[i][j] = dp[i-1][j-1] + 1;
            else
                dp[i][j] = std::max(dp[i-1][j], dp[i][j-1]);
        }
    }

    // Reconstruct and return the LCS
    std::string lcs;
    int i = m, j = n;
    while (i > 0 && j > 0) {
        if (X[i-1] == Y[j-1]) {
            lcs = X[i-1] + lcs;
            i--;
            j--;
        } else if (dp[i-1][j] > dp[i][j-1]) {
            i--;
        } else {
            j--;
        }
    }

    return lcs;
}

signed main(){
	cin.tie(nullptr)->sync_with_stdio(false);
	
	int n;
	cin >> n;
	assert(n==(int)1e6);

	string a,b;
	cin >> a >> b;
	string ans = "";
	for(int i = 0; i<n; i+=10){
		string s = a.substr(i,10);
		string t = b.substr(i,10);
		ans+= longestCommonSubsequence(s,t);
	}
	assert(ans.size() >= n/2);
	cout << ans << '\n';
	return 0;
}