#include <bits/stdc++.h>

#define ll long long
using namespace std;

void tc()
{
    int n, m;
    cin >> n >> m;
    vector<vector<char>>v(min(n, m), vector<char>(max(n, m)));

    if(n <= m)
    {
        for(int i = 0; i < n; i++)
            for(int j = 0; j < m; j++)
                cin >> v[i][j];
    }
    else
    {
        for(int i = 0; i < n; i++)
            for(int j = 0; j < m; j++)
                cin >> v[j][i];
        swap(n, m);
    }

    int waldo = 0;
    string t = "WALDO";
    for(auto& c : t)
        waldo |= (1 << (c - 'A'));


    vector<vector<vector<int>>>pref(26, vector<vector<int>>(n, vector<int>(m)));

    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
        {
            pref[v[i][j] - 'A'][i][j]++;
            if(i)
            {
                for(int c = 0; c < 26; c++)
                    pref[c][i][j] += pref[c][i - 1][j];
            }
        }
    }


    int ans = INT_MAX;
    for(int i = 0; i < n; i++)
    {
        for(int j = i; j < n; j++)
        {
            int curMsk = 0;
            vector<int>f(26);
            for(int l = 0, r = 0; l < m; l++)
            {
                while(r < m && (curMsk & waldo) != waldo)
                {
                    for(auto& c : t)
                    {
                        f[c - 'A'] += pref[c - 'A'][j][r];
                        if(i)
                            f[c - 'A'] -= pref[c - 'A'][i - 1][r];

                        if(f[c - 'A'])
                            curMsk |= (1 << (c - 'A'));
                        else if(f[c - 'A'] == 0 && (curMsk >> (c - 'A') & 1))
                            curMsk -= (1 << (c - 'A'));
                    }
                    r++;
                }

                if((curMsk & waldo) == waldo)
                    ans = min(ans, (j - i + 1) * (r - l));

                for(auto& c : t)
                {
                    f[c - 'A'] -= pref[c - 'A'][j][l];
                    if(i)
                        f[c - 'A'] += pref[c - 'A'][i - 1][l];
                    if(f[c - 'A'])
                        curMsk |= (1 << (c - 'A'));
                    else if(f[c - 'A'] == 0 && (curMsk >> (c - 'A') & 1))
                        curMsk -= (1 << (c - 'A'));
                }
            }
        }
    }

    if(ans == INT_MAX)
        cout << "impossible";
    else
        cout << ans;
}

signed main() {
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t = 1;

//    cin >> t;

    while (t--) {
        tc();
    }

    return 0;
}