#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define repr(i, n) for (int i = (int)(n - 1); i >= 0; --i)

int main() {
    int n;
    string s;
    cin >> n >> s;
    vi h;
    rep(i, n) {
        if (s[i] == '#') h.push_back(i);
    }
    int ret = 0;
    rep(k, h.size()) {
        ret = max(ret, n - h[k] + 2 * k);
    }
    cout << ret << endl;
    return 0;
}