#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
using namespace std;

int solve(string s, int pos)
{
    int n = s.size();
    int leftMost = s.find('#');

    int ans = 0;
    while(pos > leftMost){
        -- pos;
        s[pos] ^= '#' ^ '.';
        ++ ans;
    }

    int cnt = count(s.begin(), s.end(), '#');
    while(cnt > 0){
        if(pos == n - 1 || (pos > 0 && s[pos-1] == '#'))
            -- pos;
        else
            ++ pos;

        if(s[pos] == '#'){
            s[pos] = '.';
            -- cnt;
        }
        else{
            s[pos] = '#';
            ++ cnt;
        }
        ++ ans;
    }

    return ans;
}

int main()
{
    int pos;
    string s;
    cin >> pos >> s;
    -- pos;
    int n = s.size();

    int ans = solve(s, pos);
    reverse(s.begin(), s.end());
    pos = n - 1 - pos;
    ans = min(ans, solve(s, pos));
    cout << ans << endl;

    return 0;
}