def max_consec_o(s):
    max_len = 0
    current = 0
    for c in s:
        if c == 'o':
            current += 1
            if current > max_len:
                max_len = current
        else:
            current = 0
    return max_len

D = int(input())
C1 = input().strip()
C2 = input().strip()
two_weeks = C1 + C2
extended = 'x' * D + two_weeks + 'x' * D

max_run = max_consec_o(extended)

for K in range(1, D + 1):
    for i in range(len(extended) - K + 1):
        temp = list(extended)
        for j in range(i, i + K):
            if temp[j] == 'x':
                temp[j] = 'o'
        current_max = max_consec_o(''.join(temp))
        if current_max > max_run:
            max_run = current_max

print(max_run)