#include <cstdio>
#include <vector>
using namespace std;
int n,m,i,H[220],M[220][220],val=0,j,extst[220],extdr[220],k,k2,Max,posi,posj,h,lst,ldr,Max2;
char c;
vector <int> v;

int inline dreptunghi(int val)
{
    int Max=0;
    for(j=1;j<=m;++j)
            H[j]=0;
    for(i=1; i<=n; ++i)
    {
        for(j=1; j<=m; ++j)
        {
            if(M[i][j]!=val)
                H[j]=0;
            else
            {
                if(H[j]>0)
                    ++H[j];
                else H[j]=1;
            }
        }
        j=1;
        v.clear();
        while(H[j]==0 && j<=m)
            extst[j++]=0;
        if(j<=m)
        {
            extst[j]=1;
            v.push_back(j);
            ++j;
        }
        for(k=j; k<=m; ++k)
        {
            if(H[k]==0)
                extst[k]=0;
            else
            {
                v.push_back(k);
                extst[k]=1;
                while(v.size()>1 && H[v[v.size()-2]]>=H[v[v.size()-1]])
                {
                    extst[k]+=extst[v[v.size()-2]];
                    v.pop_back();
                    v.pop_back();
                    v.push_back(k);
                }
            }
        }
        j=m;
        while(H[j]==0 && j>=1)
            extdr[j--]=0;
        v.clear();
        if(j>0)
        {
            extdr[j]=1;
            v.push_back(j);
            --j;
        }
        for(k=j; k>=1; --k)
        {
            if(H[k]==0)
                extdr[k]=0;
            else
            {
                v.push_back(k);
                extdr[k]=1;
                while(v.size()>1 && H[v[v.size()-2]]<=H[v[v.size()-1]])
                {
                    extdr[k]+=extdr[v[v.size()-2]];
                    v.pop_back();
                    v.pop_back();
                    v.push_back(k);
                }
            }
        }
        for(j=1; j<=m; ++j)
            if((extst[j]+extdr[j]-1)*H[j]>Max)
            {
                Max=(extst[j]+extdr[j]-1)*H[j];
                posi=i;
                posj=j;
                h=H[j];
                lst=extst[j]-1;
                ldr=extdr[j]-1;
            }
    }
    return Max;
}
int main()
{
    freopen("bmatrix.in","r",stdin);
    freopen("bmatrix.out","w",stdout);
    scanf("%d %d\n",&n,&m);
    for(i=1; i<=n; ++i)
    {
        for(j=1; j<=m; ++j)
        {
            scanf("%c ",&c);
            M[i][j]=c-'0';
        }
        scanf("\n");
    }
    Max=dreptunghi(val);
    for(k=posi; k>=posi-h+2; --k)
        for(k2=posj-lst; k2<=posj+ldr; ++k2)
            M[k][k2]=5;
    Max2=dreptunghi(val);
    printf("%d\n",Max+Max2);
    return 0;
}