var read = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
var obj;
var inLine = [];
read.on('line', function(input){inLine.push(input);});
read.on('close', function(){
  obj = init(inLine);
  myerr("-----start-----");
  var start = new Date();
  Main();
  var end = new Date() - start;
  myerr("----- end -----");
  myerr("time : " + (end) + "ms");
});
function nextInt(){return myconv(next(),1);} function nextStrArray(){return myconv(next(),2);}
function nextIntArray(){return myconv(next(),4);} function nextCharArray(){return myconv(next(),6);}
function next(){return obj.next();} function hasNext(){return obj.hasNext();}
function init(input){  
  var returnObj = {
    list : input, index : 0, max : input.length,
    hasNext : function(){return (this.index < this.max);},
    next : function(){if(!this.hasNext()){throw "ArrayIndexOutOfBoundsException これ以上ないよ";}else{var returnInput = this.list[this.index];this.index++;return returnInput;}}
  };
  return returnObj;
}
function myout(s){console.log(s);}
function myerr(s){console.error("debug:" + require("util").inspect(s,false,null));}
//[no]要素の扱い。数値型
//不明値、異常時:引数そのまま返す 1:数値へ変換
//2:半角SPで分割 4:半角SPで分割し、数値配列へ
//6:1文字で分割  7:1文字で分割し、数値配列へ
//8:半角SPで結合 9:改行で結合 0:文字なしで結合
function myconv(i,no){try{switch(no){case 1:return parseInt(i);case 2:return i.split(" ");case 4:return i.split(" ").map(Number);case 6:return i.split("");case 7:return i.split("").map(Number);case 8:return i.join(" ");case 9:return i.join("\n");case 0:return i.join("");default:return i;}}catch(e){return i;}}
function Main(){
	var N = nextInt();
	if(N == 1){
		myout(0);
		return;
	}
	var s = next();
	var siro = new Array(N).fill(0);
	var kuro = new Array(N).fill(0);
	var output = 10000000;
	for(var i = 0; i < N; i++){
		if(s[i] == "#"){
			kuro[i]++;
		}else{
			siro[i]++;
		}
	}
	for(var i = 1; i < N; i++){
		siro[i] += siro[i - 1];
		kuro[i] += kuro[i - 1];
	}
	var siroMax = siro[N - 1];
	if(siroMax == N || siroMax == 0){
		myout(0);
		return;
	}
	if(s[0] == "#"){
		output = siroMax;
	}
	for(var i = 1; i < N; i++){
		if(s[i - 1] == "." && s[i] == "#"){
			output = Math.min(output, kuro[i - 1] + (siroMax - siro[i - 1]));
		}
	}
	myout(output);

}