/* -*- coding: utf-8 -*-
 *
 * 2035.cc:  No.2035 Tunnel - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 300000;
const int INF = 1 << 30;

/* typedef */

/* global variables */

char s[MAX_N + 4];
int xs[MAX_N], dp[MAX_N + 1];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d%s", &n, s);

  int m = 0;
  for (int i = 0; i < n; i++)
    if (s[i] == '#') xs[m++] = i;

  dp[m] = -INF;
  for (int i = m - 1; i >= 0; i--)
    dp[i] = max(dp[i + 1] + 2, n - xs[i]);

  printf("%d\n", dp[0]);
  return 0;
}