// #define _GLIBCXX_DEBUG // for STL debug (optional)
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <string>
#include <cstring>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <complex>
#include <cmath>
#include <limits>
#include <cfloat>
#include <climits>
#include <ctime>
#include <cassert>
#include <numeric>
#include <fstream>
#include <functional>
#include <bitset>
using namespace std;
using ll = long long int;
using int64 = long long int;
 
template<typename T> void chmax(T &a, T b) {a = max(a, b);}
template<typename T> void chmin(T &a, T b) {a = min(a, b);}
template<typename T> void chadd(T &a, T b) {a = a + b;}
 
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
const int INF = 1LL << 29;
const ll LONGINF = 1LL << 60;
const ll MOD = 1000000007LL;

bool is_ok(const vector<int>& A) {
    const int N = A.size();
    for(int i=0; i+1<N; i++) {
        if (A[i] == A[i+1]) return true;
    }
    return false;
}

int main() {
    int N; cin >> N;
    vector<int> A(N);
    for(auto &e : A) cin >> e;
    bool ok = false;
    for(int i=0; i+1<N; i++) {
        swap(A[i], A[i+1]);
        ok |= is_ok(A);
        swap(A[i], A[i+1]);
    }
    cout << (ok ? "Yes" : "No") << endl;
    return 0;
}