#include<bits/stdc++.h>
#define reg register
inline bool cmin(reg int &x,reg int y){return x>y?x=y,1:0;}
const int N=1010,M=N*N;
int dx[]={0,-1,0,1},dy[]={-1,0,1,0};
int id[2][N][N],cnt,tot;
int bel[M],dfn[M],dfc,vis[M],stk[M],tp,in[M],low[M];
std::vector<int> G[M],G2[M];
void tar(reg int u){
	dfn[u]=low[u]=++dfc,vis[stk[++tp]=u]=1;
	for (auto v:G[u]) if (!dfn[v]) tar(v),cmin(low[u],low[v]);
		else if (vis[v]) cmin(low[u],dfn[v]);
	if (low[u]==dfn[u]){
		++tot;
		do bel[stk[tp]]=tot,vis[stk[tp]]=0; while (stk[tp--]^u);
	}
}
int yellowblue(int n,int m,std::vector<std::string> V){
	auto chk=[&](reg int x,reg int y)->bool {return 0<=x&&x<n&&0<=y&&y<m&&V[x][y]=='.';};
	for (reg int k=0;k<2;k++) for (reg int i=0;i<n;i++) for (reg int j=0;j<m;j++) if (V[i][j]=='.')
		id[k][i][j]=chk(i+dx[k],j+dy[k])?id[k][i+dx[k]][j+dy[k]]:++cnt; 
	for (reg int k=0;k<2;k++) for (reg int i=0;i<n;i++) for (reg int j=0;j<m;j++) if (V[i][j]=='.')
		if (!chk(i+dx[k],j+dy[k])||!chk(i+dx[k+2],j+dy[k+2])) G[id[k][i][j]].push_back(id[k^1][i][j]);
	for (reg int i=1;i<=cnt;i++) if (!dfn[i]) tar(i); 
	for (reg int u=1;u<=cnt;u++) for (auto v:G[u]) if (bel[u]^bel[v]) G2[bel[u]].push_back(bel[v]),in[bel[v]]++;
	std::vector<int> ord; std::queue<int> q;
	for (reg int i=1;i<=tot;i++) if (!in[i]) q.push(i);
	while (!q.empty()){
		reg int u=q.front(); q.pop(),ord.push_back(u);
		for (auto v:G2[u]) if (!(--in[v])) q.push(v);
	}
	for (reg int i=0;i+1<ord.size();i++){
		reg int flg=0;
		for (auto v:G2[ord[i]]) flg|=v==ord[i+1];
		if (!flg) return 0;
	}
	return 1;
}