#include <iostream>
#include <vector>
#include <string>

using namespace std;

int main(void){
    int n, i, tp;
    vector<int> a;
    string ans = "No";
    
    cin >> n;
    a.clear();
    
    for (i=0; i<n; i++){
        cin >> tp;
        a.push_back(tp);
    }
    
    for (i=1; i<n; i++){
        if (a[i] == a[i-1] || i>1 && a[i] == a[i-2]) ans = "Yes";
    }
    
    cout << ans << endl;
    return 0;
}