function gameOfThrones(s){

// Complete this function

var mySet= new Set();

for(var i=0; i<s.length; i++){

mySet.add(s.charAt(i));

}

var even=0;

var odd=0;

for(var item of mySet){

var count=0;

for(var i=0; i<s.length; i++){

if(item==s[i]){

count++;

}

}

if(count%2==0){

even++;

}

else{

odd++;

}

if(s.length%2==0){

if(odd>0){

return "NO";

}

}

else{

if(odd>1){

return "NO";

}

}

}

return "YES";

}

function main() {

var s = readLine();

var result = gameOfThrones(s);

process.stdout.write("" + result + "\n");

}