#ifndef Local
#pragma GCC optimize("Ofast,no-stack-protector")
#pragma GCC target("popcnt,abm,mmx,avx2")
#endif
#include <bits/stdc++.h>

using namespace std;

#define popCnt(x) (__builtin_popcountll(x))
#define sz(x) ((int)(x.size()))
#define all(v) begin(v), end(v)
#define rall(v) rbegin(v), rend(v)
#define rep(i, l, r) for (int i = l; i < r; ++i)
using Long = long long;
using Double = double;
using vi = vector<int>;

template <class U, class V>
istream& operator>>(istream& is, pair<U, V>& p) {
  is >> p.first >> p.second;
  return is;
}
template <class T>
istream& operator>>(istream& is, vector<T>& v) {
  for (auto& x : v) {
    is >> x;
  }
  return is;
}

template <class T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  for (auto& x : v) {
    os << x << " ";
  }
  return os;
}

int h, w;
bool transpose;
string grid;

char getCell(int i, int j) {
  if (transpose) {
    return grid[j * h + i];
  }
  return grid[i * w + j];
}

string waldo = "WALDO";

int getSum(const vector<vi>& sum, int a, int b, int c, int d) {
  int res = sum[c][d];
  if (a != 0) {
    res -= sum[a - 1][d];
  }
  if (b != 0) {
    res -= sum[c][b - 1];
  }
  if (a != 0 && b != 0) {
    res += sum[a - 1][b - 1];
  }
  return res;
}

int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#ifdef Local
  freopen("test.in", "r", stdin);
  freopen("test.out", "w", stdout);
#else
#define endl '\n'
#endif
  cin >> h >> w;
  int sz = h * w;

  grid.resize(sz);
  for (char& c : grid) cin >> c;

  transpose = (h > w);
  if (transpose) swap(h, w);

  vector<vector<int>> sum[5];
  for (int i = 0; i < 5; ++i) {
    sum[i].resize(h, vi(w));
  }

  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      int c = waldo.find(getCell(i, j));
      if (c != string::npos) ++sum[c][i][j];
    }
  }

  for (int c = 0; c < 5; ++c) {
    for (int i = 0; i < h; ++i) {
      for (int j = 0; j < w; ++j) {
        if (i != 0) {
          sum[c][i][j] += sum[c][i - 1][j];
        }
        if (j != 0) {
          sum[c][i][j] += sum[c][i][j - 1];
        }
        if (i != 0 && j != 0) {
          sum[c][i][j] -= sum[c][i - 1][j - 1];
        }
      }
    }
  }

  int res = sz + 1;
  for (int i1 = 0; i1 < h; ++i1) {
    for (int i2 = i1; i2 < h; ++i2) {
      int j1 = 0;
      int j2 = 0;
      for (j1 = 0; j1 < w; ++j1) {
        for (int c = 0; c < 5; ++c) {
          while (j2 < w && getSum(sum[c], i1, j1, i2, j2) == 0) {
            ++j2;
          }
        }
        if (j2 < w) {
          res = min(res, (j2 - j1 + 1) * (i2 - i1 + 1));
        }
      }
    }
  }

  if (res > sz) {
    cout << "impossible" << endl;
  } else {
    cout << res << endl;
  }
  return 0;
}