#include<bits/stdc++.h>
using namespace std;
int main () {
    int N;
    cin >> N;
    string s;
    cin >> s;
    long long ans = 0;
    long long las = -100000000;
    long long cnt = 0;
    for (int i = N - 1; i >= 0; i --) {
        if (s[i] == '#') {
            cnt ++;
            ans = max(ans, max(las, 0ll) + N - i);
            las = max(las, 0ll) + 2;
            // ans = max(ans, (cnt*(cnt+1))/2);
        }
        las --;
    }
    cout << ans << endl;
}