var Main = function(Str){
  // var MySet = new Set();
  var Arr = Str.split("\n");
  var LL = undefined;

  for(var i=1;i<Arr[0];++i){
    var Word = Arr[i].toLowerCase();
    if(Word.length < 1 || Word.length > 10){
      console.log('No');
      return;
    }
    var F = Word.slice(0,1);
    var L = Word.slice(-1);
    // console.log(LL);
    // console.log(Word+','+F+','+L);
    // console.log('--');
    if(LL != undefined && LL !== F){
      console.log('No');
      return;
    }
    // if(MySet.has(Word)){
    //   console.log('No');
    //   return;
    // }
    // MySet.add(Word);

    for(var j=1;j<i;++j){
      if(Arr[j] == Word){
        console.log('No');
        return;
      }
    }

    LL = L;
  }
  console.log('Yes');
  return;
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));