muzikasi

#include <cstdio>
#include <queue>
using namespace std;

int n,m;
long long zbr;
char a[1007][1007];
queue <int> qx;
queue <int> qy;
int bfs ()
{
    int x,y;
    while (!qx.empty()){
          x=qx.front(); y=qy.front();
          a[x][y]='0';
          if (a[x-1][y]=='.') { qx.push (x-1); qy.push (y); a[x-1][y]='0';}
          if (a[x][y+1]=='.') { qx.push (x); qy.push (y+1); a[x][y+1]='0';}
          if (a[x+1][y]=='.') { qx.push (x+1); qy.push (y); a[x+1][y]='0';}
          if (a[x][y-1]=='.') { qx.push (x); qy.push (y-1); a[x][y-1]='0';}
          zbr++;
          qx.pop();qy.pop();
    }
}

int main ()
{
    scanf ("%d%d",&n,&m);
    for (int i=0;i<n;i++){
        scanf ("%s",a[i]);
    }
    int x,y;
    long long max=0;
    for (int i=0;i<n;i++){
        for (int j=0;j<m;j++){
            if (a[i][j]=='.'){
                qx.push (i); qy.push (j);
                bfs();
                if (zbr>max) max=zbr;
                zbr=0;
            }
        }
    }
    printf ("%I64lld",max);
}