#include<cstdio>
int max,i,j,n,m,a[1000][1000];
char c;
int main()
{
    //freopen("run.in","r",stdin);
    //freopen("run.out","w",stdout);
    scanf("%d%d\n",&n,&m);
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            scanf("%c",&c);
            if(c=='&') a[i][j]=-1;
        }
        scanf("\n");
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            if(a[i][j]!=-1)
            {
                if(a[i-1][j]+1>a[i][j]) a[i][j]=a[i-1][j]+1;
                if(a[i][j-1]+1>a[i][j]) a[i][j]=a[i][j-1]+1;
            }
        }
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
            if(max<a[i][j]) max=a[i][j];
        }
    }
    printf("%d",max);
}