var GetChars = function(word){
  return {f:word.slice(0,1), l:word.slice(-1)};
}

var Main = function(input){
  var arr = input.split('\n');
  var set = new Set();
  var latestLastChar = undefined;
  for(var i=1;i<arr.length;++i){
    var currentWord = arr[i];
    var chars = GetChars(currentWord);
    // console.log(currentWord);
    // console.log(chars);

    if(latestLastChar != undefined && latestLastChar != chars.f){
      console.log('No');
      return;
    }
    if(set.has(currentWord)){
      console.log('No');
      return;
    }
    set.add(currentWord);
    latestLastChar = chars.l;
  }
  console.log('Yes');
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));