#include <bits/stdc++.h>
using namespace std;
#define ALL(x) (x).begin(), (x).end()
#define REP(i, n) for(int i=0; i<n; i++)
bool chmax(auto& a, auto b) { return a<b ? a=b, true : false; }
bool chmin(auto& a, auto b) { return a>b ? a=b, true : false; }
using ll=long long; const int INF=1e9+10; const ll INFL=4e18;

#ifdef DEBUG
#include "./debug.hpp"
#else
#define debug(...)
#define print_line
#endif

//----------------------------------------------------------

void solve() {
    int N; cin>>N;
    vector<int> A(N); REP(i,N) cin>>A[i];

    REP(i,N-2) {
        if(A[i]==A[i+2]) {
            puts("Yes");
            return;
        }
    }
    REP(i,N-1) {
        if(A[i]==A[i+1]) {
            puts("Yes");
            return;
        }
    }
    puts("No");
}

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    //cout<<fixed<<setprecision(15);
    int T=1; //cin>>T;
    while(T--) solve();
}