Problem:
Score : 300 points

Problem Statement

There are N stones arranged in a row. Every stone is painted white or black.
A string S represents the color of the stones. The i-th stone from the left is white if the i-th character of S is ., and the stone is black if the character is #.

Takahashi wants to change the colors of some stones to black or white so that there will be no white stone immediately to the right of a black stone.
Find the minimum number of stones that needs to be recolored.

Constraints

1 \leq N \leq 2\times 10^5

S is a string of length N consisting of . and #.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the minimum number of stones that needs to be recolored.

Sample Input 1

3
#.#

Sample Output 1

1

It is enough to change the color of the first stone to white.

Sample Input 2

5
#.##.

Sample Output 2

2

Sample Input 3

9
.........

Sample Output 3

0

Solution in C (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>

int main(){
  int N;
  char S[222222];
  int i;
  scanf("%d %s",&N,S);
  int count[222222];
  count[0] = 0;
  for(i=0;i<=N-1;i++)
    if(S[i] != '#') count[0]++;
  for(i=1;i<=N;i++){
    if(S[i-1] != '#') count[i] = count[i-1] - 1;
    else count[i] = count[i-1] + 1;
    };
  int min = count[0];
  for(i=0;i<=N;i++)
    if(count[i] < min) min = count[i];
  printf("%d",min);
}