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>
#include<stdlib.h>
int main(void)
{ int n,i,pre,now,count,num;
  scanf("%d\n",&n);
char *s;
  s=(char *)malloc(sizeof(n));
 count=pre=now=num=0;
  scanf("%s\n",s);
  for(i=0;i<n;i++)
  { if(i==0)
    { if(s[i]=='#')pre=1;
      if(s[i]=='.')pre=(-1);
    }
   if(i!=0)
   {  if(s[i]=='#')now=1;
      if(s[i]=='.')now=(-1);
      if(pre>now)
      { count++;
        now=1;
      }
      pre=now;
   }
  }
 for(i=0;i<n;i++)
  { if(i==0)
    { if(s[i]=='#')pre=1;
      if(s[i]=='.')pre=(-1);
    }
   if(i!=0)
   {  if(s[i]=='#')now=1;
      if(s[i]=='.')now=(-1);
      if(pre<now)
      { num++;
        now=1;
      }
      pre=now;
   }
  }
 if(num<count)count=num;
 printf("%d\n",count);
 for(i=0;i<n;i++)printf("%c %d\n",s[i],i);
 free(s);
 return 0;
}