#include <bits/stdc++.h>

const int MAX_N = 200000;

int main() {
	int N;
	std::string S;

	std::cin >> N >> S;

	static int black[MAX_N + 1] = {};
	for(int i = 1; i <= N; ++i) {
		if(S[i - 1] == '#') black[i] = black[i - 1] + 1;
		else black[i] = black[i - 1];
	}

	int ans = MAX_N;
	for(int i = 0; i <= N; ++i) {
		ans = std::min(ans, black[i] + N - i - black[N] + black[i]);
	}

	std::cout << ans << std::endl;
}
