#![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" }
}

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

    let g = S
        .chunk_by(|a, b| a == b)
        .collect_vec();

    let mut dist = 0;
    let mut p = 0;
    let mut ans = 0;

    for (i, x) in g.iter().enumerate() {
        let w = x.len();
        if x[0] == '.' {
            let d = if i == 0 || i == g.len()-1 {
                w
            } else {
                (w+1) / 2
            };

            if dist < d {
                dist = d;
                if i == 0 {
                    ans = 0
                } else if i == g.len()-1 {
                    ans = N-1
                } else {
                    ans = p + d - 1;
                }
            }
        }

        p += x.len();
    }

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