#include <bits/stdc++.h>
using namespace std;

int main() {
    int N;
    cin >> N;
    vector<string> S(N);
    vector<char> l,r;
    char mx = 'a',res = 0;
    for(int i = 0; i < N; i++) {
        cin >> S[i];
        string T = S[i];
        sort(T.begin(),T.end());
        if(S[i] == T) {
            l.push_back(S[i][0]);
            r.push_back(S[i].back());
            if(mx == S[i][0]) {
                res++;
            }
            if(mx < S[i][0]) {
                mx = S[i][0];
                res = 1;
            }
        }
    }
    bool flag = false;
    for(int i = 0; i < l.size(); i++) {
        if(r[i] < mx) {
            flag = true;
        }
        if(l[i] == r[i] && r[i] == mx && res >= 2) {
            flag = true;
        }
    }
    cout << ((flag)?"Yes":"No") << endl;
}