function Main(input){
	input = input.split("\n");
  var list = {};
  var len = input.length;
  var lastchar = input[1][0];
  for(var i = 1; i < len;i++){
  	var text = input[i];
    if(text[0]!==lastchar)return"No";
    if(list[text])return "No";
    list[text] = 1;
    lastchar = text[text.length-1];
  }
  
  return "Yes";
}

// If you are interested in the algorithms I used, 
// there is no need to read down from this line.

((b,c,d)=>"undefined"!=typeof require?console.log(Main(require("fs").readFileSync("/dev/stdin","utf8"))):[b=b.split("\n").slice(1,-1).join("\n"),c=function(){try{return Main(b)}catch(f){return f.stack||f.message}}(),d=typeof c,"string"==d||(c=JSON.stringify(c)),$("<form>").append([[10,b],0,[1,d],0,[10,c]].map(f=>$(f?"<textarea>":"<br>",f&&{rows:f[0],cols:40,text:f[1]}))).appendTo("body")])(`
8
a
aa
aaa
aaaa
aaaaa
aaaaaa
aaa
aaaaaaa
`);