N=int(input())
S = input()

if N==1:
  print(0)
  exit()
else:
  W=[1 if S[0]=="." else 0]
  ans=float("inf")

  for i in range(1,N):
    if S[i]==".":
      W.append(W[-1]+1)
    else:
      W.append(W[-1])

  for i in range(N):
    cost_W = i+1-W[i]
    cost_B = W[-1]-W[i]
    cost=cost_W+cost_B
    #print(N, W[-1], i+1, W[i])
    #print("cost_W:",cost_W,"cost_B:",cost_B,cost)
    ans=min(ans,cost)
  
print(ans)