N = int(input())
S = input().strip()
n = S.count("#")
S = "0"+S
P = [0]*(n+1)
k = 1
for i in range(N,0,-1):
    if S[i]=="#":
        P[k] = i
        k += 1
dp = [0]*(n+1)
dp[1] = N-P[1]+1
for i in range(2,n+1):
    dp[i] = max(dp[i-1]+2,N-P[i]+1)
print(dp[n])