while(h,w=gets.split.map &:to_i)[0]>0
a=[]
b=[s=0]*w
h.times{|i|gets;a[i]=[]
w.times{|j|a[i]<<l=$_[j]<?.?0:(a[i][-1]||0)+1
m=b[j]+=l>0?1:0
l*m>s&&(1..m).map{|k|l=[l,a[i-k+1][j]].min;l*m<s ?(break):s<l*k&&s=l*k}}}
p s
end