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: Wrong Answer)


#define ll				long long
#define MOD				1000000007

#include <float.h>
#include <limits.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

int n;
char s[200010];

typedef struct data {
	int a;
	int b;
} data;

FILE *in, *ans;
int tno;


int out(const char *s) {
#ifdef TEST
	char buf[8192];
	fgets(buf, sizeof(buf), ans);
	if (strcmp(buf, s)) {
		printf("err\n");
	}
#else
	printf(s);
#endif
	return 0;
}

int outi(int i) {
	char s[128];
	sprintf(s, "%d\n", i);
	out(s);
	return 0;
}

int outll(ll l) {
	char s[128];
	sprintf(s, "%lld\n", l);
	out(s);
	return 0;
}

int geti() {
	int i;
	fscanf(in, "%d", &i);
	return i;
}

ll getll() {
	ll l;
	fscanf(in, "%lld", &l);
	return l;
}

int getstr(char *s) {
	fscanf(in, "%s", s);
	return 0;
}

int fnc() {

	int n = geti();
	getstr(s);

	int i;
	int b = 0;
	for (i = 0; i < n; i++) {
		if (s[i] == '.') {
			b++;
		}
	}

	int w = 0;
	for (i = 0; i < n - 1; i++) {
		if (s[i] == '#') {
			w++;
		}
	}

	if (b < w) {
		outi(b);
	}
	else {
		outi(w);
	}

	return 0;
}

int main() {
#ifdef TEST
	for (tno = TEST_SNO; tno <= TEST_ENO; tno++) {
		char str[128];
		sprintf(str, "test%d.txt", tno);
		in = fopen(str, "r");
		sprintf(str, "ans%d.txt", tno);
		ans = fopen(str, "r");
		fnc();
		fclose(in);
		fclose(ans);
	}
	printf("end\n");
#else
	in = stdin;
	fnc();
#endif

	return 0;
}