#include #include #include #include #include #include #include void solve() { int n; std::cin >> n; std::vector pos(n, std::valarray(n)); std::valarray row(n), col(n); for(int i : std::views::iota(0, n)) { for(int j : std::views::iota(0, n)) { char c; std::cin >> c; if((pos[i][j] = (c == '#'))) row[i] ^= 1, col[j] ^= 1; } } auto check_parity = [&]() { if(row[0] != col[0]) { std::cout << -1 << "\n"; exit(0); } for(const int i : std::views::iota(1, n)) { if(row[0] != row[i] or col[0] != col[i]) { std::cout << -1 << "\n"; exit(0); } } }; check_parity(); n--; for(int i : std::views::iota(1, n)) { for(int j : std::views::iota(0, n)) { pos[i][j] ^= pos[i - 1][j]; } } for(int i : std::views::iota(0, n)) { for(int j : std::views::iota(1, n)) { pos[i][j] ^= pos[i][j - 1]; } } std::ranges::fill(row, 0); std::ranges::fill(col, 0); for(int i : std::views::iota(0, n)) { for(int j : std::views::iota(0, n)) { if(pos[i][j]) row[i] ^= 1, col[j] ^= 1; } } if(n % 2 == 1) check_parity(); std::cout << 0 << "\n"; return; } int main() { solve(); return 0; } __attribute__((constructor)) inline void fast_io() { std::ios::sync_with_stdio(false), std::cin.tie(nullptr); }