n = int(input())
S = input()

ans = 0
cum = 0
last = -1
time = -1
for i in range(n)[::-1]:
    s = S[i]
    if s == ".":
        continue
    if last == -1:
        last = i
        time = 1
        ans = max(ans,n-i)
        # print(i,last,time,ans)
        continue

    dif = last-i
    if dif > time:
        last = i
        time = 1
        ans = max(ans,n-i)
        # print(i,last,time,ans)
        continue

    last = last-1
    
    ans = max(ans,time+n-last)
    time = time+1
    # print(i,last,time,ans)
print(ans)