def highestValuePalindrome(s, n, k):
    # Write your code here
    s=list(s)
    deduct=[0 for i in range(n)]
    # 1. make sure symmetric...deduction=[]
    curr=k
    mid=n//2
    for i in range(mid):
        if s[i] != s[n-1-i]: # need altering
            curr -= 1
            if curr<0:
                return "-1"
            deduct[i]=1
            if s[i]>s[n-1-i]:
                s[n-1-i]=s[i]
            elif s[i]<s[n-1-i]:
                s[i]=s[n-1-i]
            # print(curr,s)
    # 2. maxize...
    for i in range(mid):
        if s[i] != '9' and curr>=2-deduct[i]: # maxize and afford
            s[i] = '9'
            s[n-1-i]='9'
            curr -= (2-deduct[i])
            # print(curr,s)
            if curr==0:
                break
    # 3. special case mid
    if curr>0 and n % 2==1:
        s[mid]='9'
    return "".join(s)