process.stdin.resume();
process.stdin.setEncoding('utf8');
process.stdin.on('data', function(input) {
    var a = input.split("\n").slice(0,-1);
    var n = parseInt(a[0]);
    var w = a.slice(1);
    
    var ans = 'Yes';

    //console.log(a,n,w);
    for(var i=0; i < w.length; i++){
      for(var j=0; j < w.length-i; j++){
        //console.log(w[i],w[i+j+1])
        if( w[i] == w[i+j+1]) { ans = 'No'}
      }
    }

    for(var i=0; i < w.length-1; i++){
      if (w[i].slice(-1) != w[i+1].slice(0,1) ) {ans = 'No'}
      //console.log(w[i].slice(-1), w[i+1].slice(0,1))
    }
    console.log(ans);
} );
process.stdin.on('end', function() {
});