#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)(s); i < (int)(e); ++i)

int main() {
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
	
	int N;
	cin >> N;
	vector<int> A(N);
	rep(i, 0, N) cin >> A[i];
	
	bool find = false;
	rep(i, 0, N - 1) if (A[i] == A[i + 1]) find = true;
	rep(i, 0, N - 2) if (A[i] == A[i + 2]) find = true;
	
	cout << (find ? "Yes\n" : "No\n");
}