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