#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define ALL(a) (a).begin(), (a).end()
#define Yes cout << "Yes" << endl
#define No cout << "No" << endl

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int N;
    cin >> N;
    vector<int> A(N);
    for (auto& a : A)
        cin >> a;
    for (int i = 0; i < N - 2; i++) {
        if (A[i] == A[i + 1] || A[i] == A[i + 2]) {
            Yes;
            return 0;
        }
    }
    No;
}