#include <bits/stdc++.h>
using namespace std;

using i64 = long long;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    
    auto solve = [&]() {
        int n, m;
        cin >> n >> m;

        bool trans = false;

        if (n > m) {
            trans = true;
            swap(n, m);
        }

        vector a(n, string(m, '?'));
        for (int i = 0; i < min(n, m); i++) {
            for (int j = 0; j < max(n, m); j++) {
                if (!trans) {
                    cin >> a[i][j];
                } else {
                    cin >> a[j][i];
                }
            }
        }

        string code = "WALDO";
        vector f(5, vector(n + 1, vector<int>(m + 1)));
        
        for (int c = 0; c < 5; c++) {
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    f[c][i + 1][j + 1] = f[c][i + 1][j] + f[c][i][j + 1] - f[c][i][j] + (a[i][j] == code[c]);
                }
            }
        }

        auto sum = [&](int c, int x1, int y1, int x2, int y2) {
            return f[c][x2 + 1][y2 + 1] - f[c][x1][y2 + 1] - f[c][x2 + 1][y1] + f[c][x1][y1];
        };

        auto check = [&](int x1, int y1, int x2, int y2) {
            for (int c = 0; c < 5; c++) {
                if (sum(c, x1, y1, x2, y2) == 0) {
                    return false;
                }
            }
            return true;
        };

        constexpr int INF = 1e9;
        int ans = INF;

        for (int x1 = 0; x1 < n; x1++) {
            for (int x2 = x1; x2 < n; x2++) {
                for (int y1 = 0, y2 = 0; y1 < m; y1++) {
                    y2 = max(y2, y1);
                    while (y2 < m && !check(x1, y1, x2, y2)) {
                        y2++;
                    }
                    if (y2 < m) {
                        ans = min(ans, (x2 - x1 + 1) * (y2 - y1 + 1));
                    }
                }
            }
        }

        if (ans == INF) {
            cout << "impossible\n";
        } else {
            cout << ans << '\n';
        }
    };

    solve();

    return 0;
}