#include <bits/stdc++.h>   using namespace std;   template <class T, class U>   void ckmin(T &a, U b) {     if (a > b) a = b;   }   template <class T, class U>   void ckmax(T &a, U b) {     if (a < b) a = b;   }   int N, M;   bitset<1013> grid[1013];   int dn[1013][1013], rt[1013][1013];   int upd[1013][1013];   int x = -1, y = -1;   int ans = 998244353;   void check(int sx, int sy) {     for (auto i = (0); i < (N + 1); i++) {       for (auto j = (0); j < (M + 1); j++) {         upd[i][j] = 0;       }     }     int cx = x, cy = y;     while (true) {       upd[cx][cy]++;       upd[cx + sx][cy]--;       upd[cx][cy + sy]--;       upd[cx + sx][cy + sy]++;       if (grid[cx + sx][cy]) {         cx++;         continue;       }       if (grid[cx][cy + sy]) {         cy++;         continue;       }       break;     }     for (auto i = (0); i < (N); i++) {       for (auto j = (0); j < (M); j++) {         if (i) upd[i][j] += upd[i - 1][j];         if (j) upd[i][j] += upd[i][j - 1];         if (i && j) upd[i][j] -= upd[i - 1][j - 1];         if (upd[i][j] && !grid[i][j]) return;         if (!upd[i][j] && grid[i][j]) return;       }     }     ckmin(ans, sx * sy);   }   int32_t main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cin >> N >> M;     for (auto i = (0); i < (N); i++) {       string temps;       cin >> temps;       for (auto j = (0); j < (M); j++) {         grid[i][j] = (temps[j] ==  X );       }     }     for (auto i = (N)-1; i >= (0); i--) {       for (auto j = (M)-1; j >= (0); j--) {         if (grid[i][j]) {           x = i;           y = j;         }       }     }     for (auto i = (0); i < (N); i++) {       for (auto j = (0); j < (y); j++) {         if (grid[i][j]) {           cout <<  -1 n ;           return 0;         }       }     }     for (auto i = (0); i < (N); i++) {       for (auto j = (M)-1; j >= (0); j--) {         rt[i][j] = (grid[i][j] ? 1 + rt[i][j + 1] : 0);       }     }     for (auto i = (0); i < (M); i++) {       for (auto j = (N)-1; j >= (0); j--) {         dn[j][i] = (grid[j][i] ? 1 + dn[j + 1][i] : 0);       }     }     int dy = rt[x][y], dx = dn[x][y];     for (auto i = (x); i < (x + dx); i++) {       for (auto j = (y); j < (y + dy); j++) {         if (!grid[i][j]) {           cout <<  -1 n ;           return 0;         }       }     }     check(dx, dy);     check(dx, 1);     check(1, dy);     for (auto i = (0); i < (dy); i++) {       if (grid[x + dx][y + i]) {         check(dx, dy - i);         break;       }     }     for (auto i = (0); i < (dx); i++) {       if (grid[x + i][y + dy]) {         check(dx - i, dy);         break;       }     }     if (ans == 998244353) {       cout <<  -1 n ;       return 0;     }     cout << ans <<   n ;     return 0;   }   