#![allow(non_snake_case, unused_imports)]

use std::cmp::{min, max, Reverse};
use std::collections::{BinaryHeap, Bound, HashMap, HashSet, VecDeque};
use std::hash::Hash;
use std::ops::RangeBounds;
use ac_library::{Additive, Min, Segtree};
use proconio::{input, marker::Usize1, marker::Chars};
use itertools::Itertools;

#[allow(unused_macros)]
macro_rules! d {
    ( $( $x:expr ),* $(,)? ) => {
        eprintln!(
            concat!( $( stringify!($x), "={:?} " ),* ),
            $( $x ),*
        );
    };
}

#[allow(dead_code)]
fn yn(b: bool) -> &'static str {
    if b { "Yes" } else { "No" }
}

const INF: i64 = 1 << 62;

fn f(cs: &[char]) -> Vec<i64> {
    let mut res = vec![INF; cs.len()];

    for (i, &c) in cs.iter().enumerate() {
        if c == '#' {
            res[i] = 0;
        } else if i > 0 {
            res[i] = res[i-1] + 1;
        }
    }

    res
}

fn main() {
    input! {
        _N: usize,
        S: Chars,
    }

    let t = S.iter().rev().copied().collect_vec();

    let ls = f(&S);
    let rs = f(&t).iter().copied().rev().collect_vec();
    let mut d = 0;
    let mut ans = 0;
    for (i, (&l, &r)) in ls.iter().zip(rs.iter()).enumerate() {
        let mi = l.min(r);
        if mi > d {
            d = mi;
            ans = i;
        }
    }

    println!("{}", ans+1);
}