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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main(void)
{
	int n;
	int i;
	char a[200001];
	int co, co1, co2;

	co = co1 = co2 = 0;
	scanf("%d", &n);
	scanf("%s", a);
	for (i = 0; a[i] != '\0'; i++) {
		if (a[i] == '#') {
			co1++;
		}
		else if (a[i] == '.') {
			co2++;
		}
	}
	if (co1 > co2) {
		for (i = 0; a[i] != '\0'; i++) {
			if (a[i] == '#') {
				if (a[i + 1] == '.') {
					a[i + 1] = '#';
					co++;
				}
			}
		}
	}
	else if(co1 < co2){
		for (i = 0; a[i] != '\0'; i++) {
			if (a[i] == '.') {
				if (a[i - 1] == '#') {
					a[i - 1] = '.';
					co++;
				}
			}
		}
	}
	else if (co1 == co2) {
		for (i = 0; a[i] != '\0'; i++) {
			if (a[i] == '#') {
				if (a[i + 1] == '.') {
					if (a[i + 2] == '.') {
						a[i] = '.';
						co++;
					}
					else {
						a[i + 1] = '#';
						co++;
					}
				}
			}
		}
	}
	printf("%d\n", co);
	return 0;
}