import java.util.Arrays;
import java.util.Scanner;

public class Main86 {
	public static void main(String[] args) {
		Main86 p = new Main86();
	}

	char[][]  map;
	public Main86() {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		map = new char[n][];
		for(int i=0;i<map.length;i++)
			map[i] = sc.next().toCharArray();
		solve(n, m);
	}


	int[] dx = {-1, 0, 1, 0};
	int[] dy = {0, 1, 0, -1};
	int sx = -1;
	int sy = -1;
	public void solve(int n, int m) {
		boolean res =false;
		int tc = 0;
		for(int i=0;i<map.length;i++){
			for(int j=0;j<map[i].length;j++){
				if(map[i][j]!='.')
					continue;
					
				int d = 0;
				for(int k=0;k<4;k++){
					int nx = j+dx[k];
					int ny = i+dy[k];
					if(0<=nx && nx<map[0].length && 0<=ny && ny<map.length && map[ny][nx]=='.')
						d += (k%2==0 ? 1 : 10);
				}
				
				if(d != 11 && d!=22)
					continue;
				
				tc++;
				if(tc>10)
					break;
				for(int k=0;k<4;k++){
					sx = j;
					sy = i;
					rec(j, i, k);
					res = isOk();
				}

				if(res)
					break;
			}
			
			if(tc>10 || res)
				break;
		}
		
		System.out.println(res ? "YES" : "NO");
	}

	private boolean isOk() {
		boolean ok = true;
		for(int i=0;i<map.length;i++){
			for(int j=0;j<map[i].length;j++){
				if(map[i][j]=='.')
					ok = false;
				else if(map[i][j] == 'a')
					map[i][j] = '.';
				
			}
		}
		return ok;
	}

	private void rec(int x, int y, int curDir) {
//		System.out.println(" " + x +" " + y +" " + curDir);
//		for(int i=0;i<map.length;i++)
//			System.out.println(Arrays.toString(map[i]));
//		System.out.println();
		boolean isEnd = false;
		while(!isEnd){
			isEnd =true;
			for(int i=0;i<2;i++){
				int nx = x + dx[(curDir+i)%4];
				int ny = y + dy[(curDir+i)%4];
				
				if(nx<0 || map[0].length<=nx || ny<0 || map.length<=ny)
					continue;
				
				if(map[ny][nx]!='.')
					continue;
				
				map[ny][nx] = 'a';
				if(nx==sx && ny==sy){
					isEnd=true;
					break;
				}
				x = nx;
				y = ny;
				curDir = (curDir+i)%4;
				isEnd = false;
				break;
			}
		}
		
	}

}