euler for directed graph

string s[MAX];map<string ,int >m;map<int,string>res;int cnt,o[MAX],in[MAX],pnt,flag,start;vi v[MAX],ans;

int check(string ss)
{
    if(m[ss]==0)
    {
        m[ss] = cnt;
        res[cnt] = ss;
        cnt++;
    }
    return m[ss];
}

void again(int x)
{
    if(in[x]==o[x])return ;
    else
    {
       /// cout<<abs(in[x]-o[x])<<" "<<res[x]<<endl;
        if(abs(in[x]-o[x])>1)flag = 1;
        else if(o[x]-in[x]==1)start = x,pnt++;
        else pnt++;
    }
}

void dfs(int s)
{
    while(v[s].size())
    {
        int x = v[s][v[s].size() - 1];
        v[s].pop_back();
        dfs(x);
    }
    ans.pb(s);
}


int main()
{
    booster()
    ///read("input.txt");
    cnt = 1;
    int n;
    cin>>n;
    for(int i = 0;i<n;i++)
    {
        cin>>s[i];
        int x = check(s[i].substr(0,2));
        int y = check(s[i].substr(1,2));
        o[x]++;
        in[y]++;
        v[x].pb(y);
    }
    start = 1;
    for(int i = 1;i<=cnt;i++)
    {
        again(i);
    }
    dfs(start);
    if(flag||ans.size()!=n+1||pnt>2)cout<<"NO";
    else
    {
        cout<<"YES";
        cout<<endl;
        reverse(all(ans));
        for(int i = 0;i<ans.size();i++)
        {
            if(!i)cout<<res[ans[i]];
            else cout<<res[ans[i]][1];
        }
    }


    return 0;
}