function main(input) {
  var answer = "Yes";
  var input = input.split('\n');
  var shiritori_length = input[0];
  var shiritori_array = [];

  for (var i = 0; i < shiritori_length; i++) {
  	shiritori_array.push(input[i+1])
  	//末尾チェック
  	if(i > 0){
  		//前の語尾と先頭の文字が一致するか
  		if(shiritori_array[i-1].slice(-1) != shiritori_array[i].slice(0,1) ){
  			answer = "No";
  			break;
  		}
  		//重複チェック

	  	if(shiritori_array.slice(0,-1).includes(input[i+1])){
	  		answer = "No";
	  		break;
	  	}
  	}

  	
  }

  console.log(answer);

}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));