zerojudge_apcs_c462.py

k = int(input())
my_str = input()
canvas = [0] * len(my_str)

# step one: mark all the "switch point"
# for a example, aAbBcCdD, mark the 'a' of aA, 'A' of Ab

for i in range(len(my_str) - 1):

    if (my_str[i].islower() and my_str[i + 1].isupper()) or (my_str[i].isupper() and my_str[i + 1].islower()):
        canvas[i] = 1

# 1000010010010010000000
# AAAAAAbbbCCCdddEEEEEEE

# step 2: find the gaps that as long as K
my_str2 = ''
for i in range(len(my_str)):
    my_str2 += '_' if canvas[i] == 0 else '_ '

my_str2_arr = my_str2.split()

length = 0
max_length = 0
is_starter = True
for arr in my_str2_arr:
    if len(arr) == k:
        length += 1
        max_length = max(length, max_length)
        is_starter = False
    elif is_starter:
        if len(arr) >= k:
            length += 1
            is_starter = False
        max_length = max(length, max_length)

    else:
        if len(arr) >= k:
            length += 1
            max_length = max(length, max_length)
            length = 1
            is_starter = False
        else:
            max_length = max(length, max_length)
            length = 0
            is_starter = True

print(max_length * k)