#include <cstdio>

#include <cstring>

#include <cmath>

#include <iostream>

#include <algorithm>

#include <queue>

#include <cstdlib>

#include <vector>

#include <set>

#include <map>

#define LL long long

#define inf 1<<30

using namespace std;

char s[][],str[][];

int sum[][],l[],r[];

int n,m;

int solve(char ch,char a,char b,char c)

{

    int t;

    memset(sum,,sizeof(sum));

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

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

        {

            if(s[i][j]==a||s[i][j]==b||s[i][j]==c)str[i][j]=ch;

            else str[i][j]=s[i][j];

        }

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

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

        {

            if(str[i][j]==ch)sum[i][j]=sum[i-][j]+;

            else sum[i][j]=;

        }

    int ans=-;

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

    {

        l[]=;

        r[m]=m;

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

        {

            t=j;

            while(t>&&sum[i][j]<=sum[i][t-])t=l[t-];

            l[j]=t;

        }

        for(int j=m-; j>=; j--)

        {

            t=j;

            while(t<m&&sum[i][j]<=sum[i][t+])t=r[t+];

            r[j]=t;

        }

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

            ans=max(ans,(r[j]-l[j]+)*sum[i][j]);

    }

    return ans;

}

int main()

{

    while(scanf("%d%d",&n,&m)>)

    {

        for(int i=;i<=n;i++)scanf("%s",s[i]+);

        int ans=-;

        ans=max(ans,solve('a','w','y','z'));

        ans=max(ans,solve('b','w','x','z'));

        ans=max(ans,solve('c','x','y','z'));

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

    }

}