int A[100][100];
int tmp[100][100];
int n, m, k;

inline int INF = 1000;
inline void count1(int row, int col){
  int cnt = 0;
  for (int i = 0; i < n; ++i)
    tmp[i][col] = A[i][col];
  for (int j = 0; j < m; ++j)
    tmp[row][j] = A[row][j];
  for (int i = row - 1; i >= 0; --i)
    for (int j = col - 1; j >= 0; --j){
      if (tmp[i + 1][j + 1] == tmp[i + 1][j] && tmp[i][j + 1] == tmp[i + 1][j]) tmp[i][j] = tmp[i + 1][j];
      else if (tmp[i + 1][j] == tmp[i + 1][j + 1]) tmp[i][j] = tmp[i][j + 1];
      else if (tmp[i][j + 1] == tmp[i + 1][j + 1]) tmp[i][j] = tmp[i + 1][j];
      else tmp[i][j] = tmp[i + 1][j + 1];
      if (tmp[i][j] != A[i][j]) ++cnt;
      if (cnt > k) return INF;
    }
  for (int i = row - 1; i >= 0; --i)
    for (int j = col + 1; j < m; ++j){
      if (tmp[i + 1][j - 1] == tmp[i + 1][j] && tmp[i][j - 1] == tmp[i + 1][j]) tmp[i][j] = tmp[i + 1][j];
      else if (tmp[i + 1][j] == tmp[i + 1][j - 1]) tmp[i][j] = tmp[i][j - 1];
      else if (tmp[i][j - 1] == tmp[i + 1][j - 1]) tmp[i][j] = tmp[i + 1][j];
      else tmp[i][j] = tmp[i + 1][j - 1];
      if (tmp[i][j] != A[i][j]) ++cnt;
      if (cnt > k) return INF;
    }
  for (int i = row + 1; i < n; ++i)
    for (int j = col - 1; j >= 0; --j){
      if (tmp[i - 1][j + 1] == tmp[i - 1][j] && tmp[i][j + 1] == tmp[i - 1][j]) tmp[i][j] = tmp[i - 1][j];
      else if (tmp[i - 1][j] == tmp[i - 1][j + 1]) tmp[i][j] = tmp[i][j + 1];
      else if (tmp[i][j + 1] == tmp[i - 1][j + 1]) tmp[i][j] = tmp[i - 1][j];
      else tmp[i][j] = tmp[i + 1][j + 1];
      if (tmp[i][j] != A[i][j]) ++cnt;
      if (cnt > k) return INF;
    }
  for (int i = row + 1; i < n; ++i)
    for (int j = col + 1; j < m; ++j){
      if (tmp[i - 1][j - 1] == tmp[i - 1][j] && tmp[i][j - 1] == tmp[i - 1][j]) tmp[i][j] = tmp[i - 1][j];
      else if (tmp[i - 1][j] == tmp[i - 1][j - 1]) tmp[i][j] = tmp[i][j - 1];
      else if (tmp[i][j - 1] == tmp[i - 1][j - 1]) tmp[i][j] = tmp[i - 1][j];
      else tmp[i][j] = tmp[i - 1][j - 1];
      if (tmp[i][j] != A[i][j]) ++cnt;
      if (cnt > k) return INF;
    }
}
inline void solve1(){
  int ans = INF;
  for (int i = 0; i < n; ++i)
    for (int j = 0; j < m; ++j){
      int mb = count1(i, j);
      mn(ans, mb);
    }
  if (ans == INF) ans = -1;
  cout << ans << endl;
}