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#include <bits/stdc++.h>
using namespace std;

vector<int> suffix_array(string& S) {
	int N = S.length();
	vector<int> SA(N), rank(N);
	for (int i = 0; i < N; i++) {
		SA[i] = N - i - 1;
		rank[i] = S[i];
	}
	stable_sort(SA.begin(), SA.end(), [&S](int i, int j) { return S[i] < S[j]; });
	for (int t = 1; t < N; t <<= 1) {
		vector<int> tmp(rank);
		for (int i = 0; i < N; i++) {
			bool s = i && SA[i - 1] + t < N && tmp[SA[i]] == tmp[SA[i - 1]] && tmp[SA[i] + (t >> 1)] == tmp[SA[i - 1] + (t >> 1)];
			rank[SA[i]] = s ? rank[SA[i - 1]] : i;
		}
		tmp = SA;
		vector<int> cnt(N);
		for (int i = 0; i < N; i++) cnt[i] = i;
		for (int i = 0; i < N; i++) {
			if (tmp[i] >= t) SA[cnt[rank[tmp[i] - t]]++] = tmp[i] - t;
		}
	}
	return SA;
}

vector<int> lcp_array(const vector<int>& SA, string& S) {
	int N = S.size();
	vector<int> rank(N), LCP(N - 1);
	for (int i = 0; i < N; i++) rank[SA[i]] = i;
	int pre = 0;
	for (int i = 0; i < N; i++) {
		if (rank[i] < N - 1) {
			int j = SA[rank[i] + 1];
			while (max(i, j) + pre < S.size() && S[i + pre] == S[j + pre]) pre++;
			LCP[rank[i]] = pre;
			if (pre > 0) pre--;
		}
	}
	return LCP;
}

int main() {
	int A, B;
	string X, Y;
	cin >> A >> B >> X >> Y;
	string S = X + '$' + Y;
	vector<int> SA = suffix_array(S);
	vector<int> L = lcp_array(SA, S);
	int ans = 0;
	for (int i = 0; i < S.size() - 1; ++i) {
		if ((SA[i] < A && SA[i + 1] > A) || (SA[i] > A && SA[i + 1] < A)) {
			ans = max(L[i], ans);
		}
	}
	cout << ans << '\n';
}