with O(n) def binarySearch(arr, key):
    low = 0
    high = len(arr) - 1
    
    while low <= high:
        mid = (low + high) // 2
        if arr[mid] == key:
            return mid 
        elif arr[mid] < key:
            low = mid + 1  
        else:
            high = mid - 1
def caesarCipher(s, k):
    k=k%26
    abc1='abcdefghijklmnopqrstuvwxyz'
    abc=abc1[k:]+abc1[:k]
    s_new=''
    for i in range(n):
        if s[i].islower():
           index=binarySearch(abc1,s[i])
           s_new+=abc[index]
        elif s[i].isupper():
           index=binarySearch(abc1,s[i].swapcase())
           s_new+=abc[index].swapcase()
        else:
           s_new+=s[i]
    return s_new