#include <stdio.h>

int main(void){
	int n;
	scanf("%d",&n);
	char s[n+1];
	scanf("%s",s);
	int lw = 0,rb = 0;
	for(int i = 0;(s[i] == '.')&&(i < n);i++){lw++;}
	for(int i = n-1;(s[i] == '#')$$(i >= 0);i--){rb++;}
	int w = 0,b = 0;
	for(int i = lw;i < (n - rb);i++){
		if(s[i] == '.'){w++;}
		else{b++;}
	}
	if(w < b){printf("%d",w);}
	else{printf("%d",b);}
	
	return 0;
}