public static String isValid(String s) {
    // Write your code here
    int freq=0,count=0;
    Map<Character,Integer> frqMap = new HashMap<Character,Integer>();
    Map<Integer,Integer> higMap=new HashMap<>();
    for(char c: s.toCharArray()){
        frqMap.put(c, frqMap.getOrDefault(c, 0)+1);
    }
    
    for(int i:frqMap.values()){
        higMap.put(i, higMap.getOrDefault(i, 0)+1);
    }
    
    for(int i:higMap.keySet()){
        if(freq<higMap.get(i))
            freq=i;
    }
    
    
    for(int i: frqMap.values()){
        if(i!=freq){
            if(i==1)
                count++;
            else if(i<freq)
                count+=freq-i;
            else
                count+=i-freq;
        }
    }    
    
    if(count>1)
        return "NO";
    else
        return "YES";

    }