# coding: utf-8
# Your code here!
N = int(input())
S = input()
black = 0
white = 0
l = [] # 
 
for s in S:
    if s == "#":
        black += 1
    else:
        white += 1
 
if white == 0:
    print(0)
    
else:
    leftBlack = 0
    rightWhite = white
    for s in S:
        if s == "#":
            leftBlack += 1
        else:
            rightWhite -= 1
            
        l.append(leftBlack + rightWhite)
        
    print(min(l))