wordgame

//#include<bits/stdc++.h>
#include<iostream>
#include<unordered_map>

#define long long long
#define nln '\n'

using namespace std;

long n;

int main()
{
    cin >> n;
    string st1 = "" , st2 = "";
    bool fal = 0;
    unordered_map<string, bool > dic;
    long loc = 0;

    for (long i = 1; i <= n; ++i)
    {
        cin >> st2;
        if (st1 == "")
        {
            dic[st2] = 1;
            st1 = st2;
            continue;
        }

        if (st2[0] != st1[st1.size()-1] || dic[st2])
        {
            loc = i;
            fal = 1;
            break;
        }
        dic[st2] = 1;
        st1 = st2;
    }

    if (!fal)
        cout << "YES" << nln;
    else
    {
        cout << "NO" << nln;
        cout << loc << nln;
    }
    return 0;
}