import sys
from collections import deque
import copy
import math
def get_read_func(fileobject):
    if fileobject == None :
        return raw_input
    else:
        return fileobject.readline



def main():
    if len(sys.argv) > 1:
        f = open(sys.argv[1])
    else:
        f = None
    read_func = get_read_func(f);
    input_raw = read_func().strip().split()
    [N] = [int(input_raw[0])]
    input_raw = read_func().strip().split()
    S = input_raw[0]

    new_S1 = ""
    new_S2 = ""
    flag = False
    for i in range(N):
        if S[i] == "." and flag == False:
            new_S1 += "."
        else:
            new_S1 += "#"
            flag = True

    flag = False
    for i in range(N):
        if S[N - i - 1] == "#" and flag == False:
            new_S2 += "#"
        else:
            new_S2 += "."
            flag = True
    count1 = 0
    count2 = 0
    new_S2 = new_S2[::-1]
    for i in range(N):
        if S[i] != new_S1[i]:
            count1 += 1
        if S[i] != new_S2[i]:
            count2 += 1
    print min(count1, count2)


if __name__ == '__main__':
    main()
