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: Runtime Error)

#include<stdio.h>
int MIN(int a,int b){return a<b?a:b;}
int main(){
  int n,i,b[100010]={};
  char s[100010];
  int m=1e9,w[100010]={};
  scanf("%d %s",&n,s);
  for(i=0;i<n;i++)w[i+1]=w[i]+(s[i  ]=='#'?1:0);
  for(i=n;i  ;i--)b[i-1]=b[i]+(s[i-1]=='.'?1:0);
  //for(i=0;i<=n;i++)printf("%d %d\n",b[i],w[i]);
  for(i=0;i<=n;i++)m=MIN(m,b[i]+w[i]);
  printf("%d\n",m);
  return 0;
}