o12_oct_box

#include <bits/stdc++.h>

using namespace std;
using pi = pair <int, int>;
const int N = 30 + 10;
const int M = 30 + 10;
char ar[N][M];
bool vs[N][M];
int n, m;

bool Pst(int i, int j){
    return 1 <= i and i <= n and 1 <= j and j <= m;
}

bool Box(int ui, int uj){
    if(!Pst(ui, uj) or ar[ui][uj] == '#') return false;
    if(!Pst(ui + 1, uj) or ar[ui + 1][uj] == '#') return false;
    if(!Pst(ui, uj + 1) or ar[ui][uj + 1] == '#') return false;
    if(!Pst(ui + 1, uj + 1) or ar[ui + 1][uj + 1] == '#') return false;
    return true;
}

int main(){

    scanf("%d %d", &n, &m);

    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            scanf(" %c", &ar[i][j]);
        }
    }

    queue <pi> q;
    for(int j=1;j<=m;j++){
        if(Box(1, j))
            q.push({1, j});
    }

    while(!q.empty()){
        int ui = q.front().first;
        int uj = q.front().second;
        q.pop();
        if(vs[ui][uj])
            continue;
        vs[ui][uj] = true;
        if(ui == n - 1){
            printf("yes");
            return 0;
        }
        if(Box(ui - 1, uj)) q.push({ui - 1, uj});
        if(Box(ui + 1, uj)) q.push({ui + 1, uj});
        if(Box(ui, uj - 1)) q.push({ui, uj - 1});
        if(Box(ui, uj + 1)) q.push({ui, uj + 1});
    }

    printf("no");

    return 0;
}