h,w=map(int,input().split())
X=[]
ans=100000
for i in range(h):
    s=input()
    X.append(s)
    cnt=0
    for j in s:
        if j=="." and cnt!=0:
            ans=min(ans,cnt)
            cnt=0
        if j=="#":
            cnt+=1
    if cnt!=0:
        ans=min(ans,cnt)
for i in range(w):
    cnt=0
    for j in range(h):
        key=X[j][i]
        if key=="." and cnt!=0:
            ans=min(ans,cnt)
            cnt=0
        if key=="#":
            cnt+=1
    if cnt!=0:
        ans=min(ans,cnt)
print(ans)