#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }
#define sz(x) (int)x.size()
#define all(x) x.begin(),x.end()
#define gtr(T) vector<T>,greater<T>
#define int long long
using namespace std;
using namespace __gnu_pbds;
template<class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

void err(istream_iterator<string> it) { cerr << endl; }

template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
    cerr << *it << " = " << a << endl;
    err(++it, args...);
}

#define S second
#define F first
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
const int N = 2005;
const string TARGET = "WALDO";

vector<vector<char> > a;
vector<vector<int> > pref[5];
int n, m;

vector<vector<int> > build(char c) {
    vector<vector<int> > pref(n + 1, vector<int>(m + 1, 0));
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            pref[i][j] = (a[i][j] == c) + pref[i - 1][j] + pref[i][j - 1] - pref[i - 1][j - 1];
        }
    }
    return pref;
}

int get(int r, int r2, int c, int c2, int idx) {
    return pref[idx][r2][c2] - pref[idx][r - 1][c2] - pref[idx][r2][c - 1] + pref[idx][r - 1][c - 1];
}

bool check(int r, int r2, int c, int c2) {
    for (int i = 0; i < 5; i++) {
        if (get(r, r2, c, c2, i) == 0) return 0;
    }
    return 1;
}

signed main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cin >> n >> m;
    a = vector<vector<char>>(min(n + 1, m + 1), vector<char>(max(n + 1, m + 1)));
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (n < m) cin >> a[i][j];
            else cin >> a[j][i];
        }
    }
    if (n > m) swap(n, m);
    for (int i = 0; i < 5; i++) pref[i] = build(TARGET[i]);
    ll ans = n * m + 1;
    for (int r1 = 1; r1 <= n; r1++)
        for (int r2 = r1; r2 <= n; r2++)
            for (int c1 = 1, c2 = 1; c1 <= m; c1++) {
                while (c2 <= m && !check(r1, r2, c1, c2))c2++;
                if (c2 <= m) {
                    ans = min(ans, (r2 - r1 + 1) * (c2 - c1 + 1));
                }
            }

    if (ans > n * m) cout << "impossible\n";
    else
        cout << ans << '\n';
}