import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

D = int(readline())
C = ''.join(read().decode().split())

answer = 0
for n in range(15):
    for i in range(14):
        if i + n > 14:
            break
        x = C[i:i+n].count('x')
        if x <= D:
            answer = n

print(answer)