#include<iostream>
#include<string>
using namespace std;
 
int main()
{
    int N;
    cin >> N;
    string S;
    for(int i = 0; i < N; i++) 
    {
        cin >> S;
    }
    for(int i = 1; i < N; i++)
    {
        if(S[i] == S[i-1]) 
        {
            cout << "No" << endl;
            return 0;
        }
    }
    cout << "Yes" << endl; 
    return 0;
}