#include <bits/stdc++.h>

using namespace std;

int main() {
    int N;
    cin >> N;

    string S;
    cin >> S;

    int magic = 0;

    int s = 0, r = N + 1;

    for (int i = N - 1; i >= 0; i--) {
        if (S[i] == '#') {
            s = max(s - (r - i - 1), 0);
            r = i;
            magic = max(magic, s + N - i);
            ++s;
        }
    }

    cout << magic << endl;

    return 0;
}