// <2630.cpp> - Tue Oct 18 20:36:24 2016

// This file is made by YJinpeng，created by XuYike's black technology automatically.

// Copyright (C) 2016 ChangJun High School, Inc.

// I don't know what this program is.

#include <iostream>

#include <cstring>

#include <cstdio>

#include <cmath>

using namespace std;

const int MAXN=;

int g[MAXN],f[MAXN][MAXN];

int main()

{

    freopen("2630.in","r",stdin);

    freopen("2630.out","w",stdout);

    int n,m,ans=;scanf("%d%d",&n,&m);

    for(int i=;i<=n;i++)

        for(int j=;j<=m;j++){

            char ch=getchar();

            while(ch!=''&&ch!='')ch=getchar();

            f[i][j]=f[i-][j]+(ch==''?-:);

        }

    for(int i=;i<=n;i++)

        for(int j=i;j<=n;j++)

            for(int k=;k<=m;k++)

                g[k]=(g[k-]<?:g[k-])+f[j][k]-f[i-][k],ans=max(g[k],ans);

    printf("%d\n",ans);

    return ;

}