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;
  scanf("%d", &n);
 
  char s[n+2];
  scanf("%s",s);
 
  int stone[n][2];
 
  int i,white=0,black=0;
 
  for(i= 0;i<n;i++){
    if(s[i]=='#'){
      black++;
    } else {
      white++;
    }
    stone[i][0] = white;
    stone[i][1] = black;
  }
 
 /*int min = white;
 if(b<min) min = black;*/
  int min=(black>white)?white:black;
 
 for(i=0;i<n;i++){
   if(min>white-stone[i][0]+stone[i][1]) 
     min=white-stone[i][0]+stone[i][1];
 }
 
 printf("%d\n", min);
 
 return 0;
}