#include<bits/stdc++.h>
using namespace std;

#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

#define mygc(c) (c)=getchar_unlocked()
#define mypc(c) putchar_unlocked(c)

void reader(int *x){int k,m=0;*x=0;for(;;){mygc(k);if(k=='-'){m=1;break;}if('0'<=k&&k<='9'){*x=k-'0';break;}}for(;;){mygc(k);if(k<'0'||k>'9')break;*x=(*x)*10+k-'0';}if(m)(*x)=-(*x);}
int reader(char c[]){int i,s=0;for(;;){mygc(i);if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF) break;}c[s++]=i;for(;;){mygc(i);if(i==' '||i=='\n'||i=='\r'||i=='\t'||i==EOF) break;c[s++]=i;}c[s]='\0';return s;}
template <class T, class S> void reader(T *x, S *y){reader(x);reader(y);}

void writer(const char x[], char c){int i;for(i=0;x[i]!='\0';i++)mypc(x[i]);mypc(c);}
template<class T> void writerLn(T x){writer(x,'\n');}

#define MD 1000000007

int N, M;
char mp[1000][1000];

int dx[4] = {-1,0,1,0}, dy[4] = {0,-1,0,1};
int s, t, nn;

void nul(int a, int b, int d){
  int i, na, nb;

  rep(i,2){
    na = a + dx[(d+i)%4];
    nb = b + dy[(d+i)%4];
    if(na < 0 || nb < 0 || na >= N || nb >= M) continue;
    if(mp[na][nb] != '.') continue;
    mp[na][nb] = '@'; nn++;
    if(na==s && nb==t) break;
    nul(na,nb,(d+i)%4);
    break;
  }
}

void del(int a, int b){
  int i, na, nb;

  if(mp[a][b] != '@') return;
  mp[a][b] = '.';
  
  rep(i,4){
    na = a + dx[i];
    nb = b + dy[i];
    if(na < 0 || nb < 0 || na >= N || nb >= M) continue;
    del(na,nb);
  }
}

int main(){
  int i, j, k, d, a, b, ok = 0;
  int cnt = 0;

  reader(&N,&M);
  rep(i,N) reader(mp[i]);

  rep(i,N) rep(j,M) if(mp[i][j]=='.') cnt++;
  if(cnt > 4*(N+M)){ writerLn("NO"); return 0; }

  rep(i,N) rep(j,M) if(mp[i][j]=='.') rep(d,4) if(!ok){
    s=i; t=j; nn = 0;
    nul(i,j,d);
    if(nn==cnt){ ok=1; break; }
    mp[i][j]='@'; del(i,j);
  }

  writerLn(ok?"YES":"NO");

  return 0;
}