from collections import Counter

def isValid(s):
    sv = sorted(Counter(s).values())  # Count character frequencies and sort them
    
    # If all frequencies are the same, it's valid
    if len(set(sv)) == 1:
        return "YES"
    
    # Check cases where one frequency can be removed or adjusted to match the others
    if sv[0] == 1 and sv[1] == sv[-1]:
        return "YES"
    
    # Check if we can make it valid by reducing the highest frequency by one
    if sv[-1] - sv[-2] == 1 and sv[0] == sv[-2]:
        return "YES"
    
    return "NO"

from collections import Counter

def isValid(s):
    c = dict(sorted(Counter(Counter(s).values()).items()))
    return 'YES' if (len(c) == 1 or (len(c) == 2 and ((list(c.keys())[1] - list(c.keys())[0] == 1 and list(c.values())[1] == 1) or c.get(1) == 1))) else 'NO'

public static String isValid(String s) {
        if (s.length()==1)
            return "YES" ;
        // Count the letters 
        int[] l = new int[26] ;
        for (int i=0; i<s.length(); ++i) {
            ++l[s.charAt(i)-97];
        }
        
        // Sort the Letter count
        Arrays.sort(l);
        
        // Check for deviation.
        boolean hasAdjusted = false ;
        int goal = (l[l.length-1]!=l[l.length-2])?l[l.length-2]:l[l.length-1];
        for (int i=l.length-1; i>=0; --i) {
            if (l[i] != 0 ) {
                if (l[i] > goal) {
                    if (hasAdjusted || l[i] - goal > 1)
                        return "NO";
                    hasAdjusted = true;
                } else if (l[i] < goal) {
                    if ( hasAdjusted || l[i] != 1)
                        return "NO";
                    hasAdjusted=true;
                }
            }
        }
        
        return "YES" ;
    }

public static String isValid(String s) {
        // Write your code here
        HashSet <Character> stringSet = new HashSet<>();
        List <Character> stringList = new ArrayList<>();
        HashMap <Character, Integer> frequency = new HashMap<>();
        HashMap <Integer, Integer> freqCount = new HashMap<>();
        for (char c : s.toCharArray()) {
            stringSet.add(c);
            stringList.add(c);
        }
        for (Character ch : stringSet) {
            frequency.put(ch, Collections.frequency(stringList, ch));
        }
        int size = new HashSet<>(frequency.values()).size();
        if (size == 1) {
            return "YES";
        } 
        for (Integer value : frequency.values()) {
            freqCount.put(value, freqCount.getOrDefault(value, 0) + 1);
        }
        if (freqCount.size() == 2) {
            if (Collections.min(freqCount.keySet()) == 1 && freqCount.get(Collections.min(freqCount.keySet())) == 1) {
                return "YES";
            } else if (Collections.max(freqCount.keySet())-Collections.min(freqCount.keySet())==1 && freqCount.get(Collections.max(freqCount.keySet())) == 1) {
                return "YES";
            } else {
                return "NO";
            }
        }
        return "NO";
    }