# from scipy.sparse import csr_matrix
# import string
import sys

sys.setrecursionlimit(10 ** 5 + 10)


def input(): return sys.stdin.readline().strip()


def resolve():
    N = int(input())
    S = list(input())

    B=[0]*N
    W=[0]*N

    cntb=0
    cntw=0
    for i in range(N):
        if S[i]=='#':
            cntb+=1
            B[i]=cntb
            W[i]=cntw
        else:
            cntw+=1
            B[i]=cntb
            W[i]=cntw
    B=[0]+B
    W=[0]+W

    ans=10**9
    for i in range(1,N+1):
        ans=min(ans,B[i]+W[-1]-W[i])
    print(ans)






resolve()