#include <iostream>
#include <string>
 
using namespace std;
 
int main(void)
{
	int N;
	cin >> N;
 
	string arr;
	cin >> arr;
 
	int min = N;		//거리 최솟값
	int first;			//왼쪽에 있는 공석 위치
	int last;			//오른쪽에 있는 공석 위치
	for (int i = 0; i < arr.length(); i++)	//첫 번째 공석 위치 찾기
	{
		if (arr[i] == '.') {
			first = i;
			break;
		}
	}
 
	for (int i = first + 1; i < arr.length(); i++)
	{
		if (arr[i] == '.') {				//오른쪽에 있는 공석 위치 찾기
			last = i;
			if (min > last - first - 1)		//거리의 차이가 최솟값보다 더 작다면 저장
				min = last - first - 1;
			first = last;					//오른쪽에 있는 공석의 위치를 왼쪽에 있는 공석의 위치로 지정
		}
	}
	cout << min;							//최솟값 출력
}

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

NQojLiMjLg==

5
#.##.